FOR PUBLICATION
  UNITED STATES COURT OF APPEALS
       FOR THE NINTH CIRCUIT

ENGINE MANUFACTURERS                   
ASSOCIATION,
                Plaintiff-Appellant,
                v.
SOUTH COAST AIR QUALITY
MAINTENANCE DISTRICT,
(SCAQMD); WILLIAM A. BURKE,
SCAQMD Board Chairman;
NORMA J. GLOVER, SCAQMD
Vice-Chairman; MICHAEL D.
ANTONOVICH, SCAQMD Board
Member; HAL BERNSON, SCAQMD                  No. 05-56654
Board Member; JANE W. CARNEY,
SCAQMD Board Member;                          D.C. No.
                                           CV-00-09065-FMC
CYNTHIA P. COAD, SCAQMD
Board Member; BEATRICE J.S.                   OPINION
LAPISTOKIRTLEY, SCAQMD Board
Member; RONALD O. LOVERIDGE,
SCAQMD Board Member; JON D.
MIKELS, SCAQMD Board
Member; LEONARD PAULITZ,
SCAQMD Board Member;
CYNTHIA VERDUGO-PERALTA,
SCAQMD Board Member; S. ROY
WILSON, SCAQMD Board
Member; BARRY R. WALLERSTEIN,
SCAQMD Executive Officer;
             Defendants-Appellees,
                                       


                            10125
10126           ENGINE MFRS. ASS’N v. SCAQMD


NATURAL RESOURCES DEFENSE              
COUNCIL; COALITION FOR CLEAN
AIR, INC.; COMMUNITIES FOR A
BETTER ENVIRONMENT;
PLANNING AND CONSERVATION
LEAGUE; SIERRA CLUB,
            Defendants-Intervenors-
                          Appellees,
                                       
                 v.
WESTERN STATES PETROLEUM
ASSOCIATION,
               Plaintiff-Intervenor-
                          Appellant.
                                       
          Appeal from the United States District Court
              for the Central District of California
        Florence Marie Cooper, District Judge, Presiding

                     Argued and Submitted
              July 10, 2007—Pasadena, California

                     Filed August 20, 2007

   Before: Barry G. Silverman, William A. Fletcher, and
            Richard R. Clifton, Circuit Judges.

             Opinion by Judge William A. Fletcher
10130          ENGINE MFRS. ASS’N v. SCAQMD
                          COUNSEL

Timothy A. French, Neal, Gerber and Eisenberg, Chicago,
Illinois, for the appellant.

Fran M. Layton, Shute, Mihaly and Weinberger, San Farn-
cisco, California; Kurt R. Wiese, SCAQMD, Diamond Bar,
California; Daniel P. Selmi, Los Angeles, California, for the
appellees.

Julie Masters, Melissa L. Perrella, NRDC, Santa Monica, Cal-
ifornia, for the defendant-intervenors-appellees.

Michael R. Barr, Kevin M. Fong, Pillsbury Winthrop, San
Francisco, California; Mark E. Elliott, Pillsbury Madison, et
al., Los Angeles, California, for the plaintiff-intervenor-
appellant.

Kipp A. Coddington, Alston & Bird, Washington, D.C.;
Timothey J. Dowling, Community Rights Counsel, Washing-
ton, D.C.; Susan L. Durbin, Office of California Attorney
General, Sacramento, California, for the amici curiae.


                          OPINION

W. FLETCHER, Circuit Judge:

   Defendant-appellee South Coast Air Quality Management
District (“the District”) is a political subdivision of the State
of California responsible for air pollution control in the South
Coast Air Basin (“the Basin”), an area comprising the City of
Los Angeles and portions of surrounding counties. In 2000,
the District enacted six “Fleet Rules” that require operators of
various kinds of vehicle fleets — such as street sweepers, gar-
bage trucks, and airport shuttles — to choose vehicles meet-
ing specified emissions standards or containing specified
               ENGINE MFRS. ASS’N v. SCAQMD               10131
alternative-fuel engines when adding to their fleets. Some
provisions of the Fleet Rules apply to state and local govern-
mental agencies; others apply to federal governmental agen-
cies and to private fleet operators. After a remand by the
Supreme Court, we consider for the second time whether
these Fleet Rules are preempted by the federal Clean Air Act
(“CAA”), 42 U.S.C. §§ 7401 et seq.

   We have jurisdiction under 28 U.S.C. § 1291. We review
de novo the district court’s grant of summary judgment,
including its preemption analysis. See Chamber of Commerce
v. Lockyer, 

, 1082 (9th Cir. 2006) (en banc).
We affirm the district court in part, reverse in part, and
remand for further proceedings.

                       I.   Background

   The Basin is the only area in the United States classified by
the Environmental Protection Agency as an extreme nonat-
tainment area for ozone. It is one of only five areas designated
as a serious non-attainment area for small particulate matter.
See 42 U.S.C. §§ 7511(a), 7513(b).

   The District is charged with developing and implementing
strategies to meet air quality standards within the Basin. See
Cal. Health & Safety Code §§ 40404, 40412, 40440. Califor-
nia Health and Safety Code § 40447.5, adopted in 1987,
authorizes the District to adopt regulations that

    [r]equire operators of public and commercial fleet
    vehicles, consisting of 15 or more vehicles under a
    single owner or lessee and operating substantially in
    the south coast district, when adding vehicles to or
    replacing vehicles in an existing fleet or purchasing
    vehicles to form a new fleet, to purchase vehicles
    which are capable of operating on methanol or other
    equivalently clean burning alternative fuel and to
    require that these vehicles be operated, to the maxi-
10132           ENGINE MFRS. ASS’N v. SCAQMD
    mum extent feasible, on the alternative fuel when
    operating in the south coast district.

   Between June and October 2000, the District adopted six
rules (the “Fleet Rules” or “Rules”) pursuant to § 40447.5.
Each Rule applies only to fleet operators of 15 or more vehi-
cles. The Rules variously refer to “purchasing,” “procuring,”
“leasing,” and “contracting for” vehicles and appear to use the
terms “purchasing” and “procuring” interchangeably. In order
to be as clear as possible in our holding, and at the risk of
awkward repetition, we adhere to the Rules’ terminology
throughout this opinion.

   Fleet Rule 1186.1 applies to fleet operators of street sweep-
ers “when purchasing or leasing these vehicles for sweeping
operations undertaken by or for governments or governmental
agencies in the jurisdiction of [the District].”] The Rule
applies to (1) “any federal, state, county, city or governmental
department or agency, [and] any special district such as water,
air, sanitation, transit, and school districts” (hereinafter, “pub-
lic fleets”); and (2) any “private individual firm, association,
franchise, contractor, user or owner who provides sweeping
services to a governmental agency” (hereinafter, “private
fleets with public contracts”). When purchasing or leasing
street sweepers, these fleet operators must “acquire
alternative-fuel or otherwise less-polluting sweepers.” An
“alternative-fuel sweeper” is one with “engine(s) that use
compressed or liquefied natural gas, liquefied petroleum gas
(propane), methanol, electricity, or fuel cells,” and “[h]ybrid-
electric and dual-fuel technologies that use diesel fuel are not
considered alternative-fuel technologies for the purposes of
[the] rule.” Fleet operators may obtain a waiver from the
Rule’s requirement if they “demonstrate the technical infeasi-
bility of complying” either because no such sweepers are
commercially available, or because a fueling station for
alternative-fuel sweepers is “not available within five miles of
               ENGINE MFRS. ASS’N v. SCAQMD              10133
the vehicle storage or maintenance yards.” Rule 1186.1 also
requires government agencies that contract for sweeping ser-
vices to contract for sweeping services that use alternative-
fuel sweepers if possible.

   Fleet Rule 1191 applies to public fleets located in the
Basin. It “requires passenger car, light-duty truck, or medium-
duty vehicle fleet operators to acquire low-emitting gasoline
or alternative-fuel vehicles . . . when procuring or leasing
these vehicles in the District.” The Rule defines compliant
vehicles by reference to emissions standards for low-emission
vehicles set by the California Air Resources Board (“CARB”)
pursuant to California’s preemption waivers under § 209(b) of
the Clean Air Act (discussed in greater detail below). The
Rule contains various exemptions, including an exemption for
emergency vehicles. The Rule also allows the public fleets to
continue to purchase gasoline- or diesel-fueled vehicles by
“offsetting” those purchases with purchases of low emission
vehicles. The Rule does not apply to “[p]rivately owned or
operated light- or medium-duty fleets that provide contract
services to [a] public agency.”

   Fleet Rule 1192 applies to fleets of “public transit vehi-
cle[s] or urban buses, operated by government agencies or
operated by private entities under contract to government
agencies.” When procuring or leasing vehicles, these fleet
operators must choose “alternative-fuel heavy-duty vehicles,”
defined as vehicles “that use[ ] compressed or liquified natu-
ral gas, propane, methanol, electricity, fuel cells, or other
advanced technologies that do not rely on diesel fuel,” and
that meet the emissions requirements of the Urban Transit
Bus Rule adopted by CARB. The Rule contains various
exemptions, including for buses “not used for the express pur-
pose of public transportation” and for buses “used for the
express[ ] purpose of providing long-distance service (out-of-
District).”

  Fleet Rule 1193 applies to both public and private fleets of
garbage trucks, regardless of whether the private fleets are
10134           ENGINE MFRS. ASS’N v. SCAQMD
under public contract. The Rule requires the “fleet operators
to acquire alternative-fuel refuse collection heavy-duty vehi-
cles when procuring or leasing these vehicles” and defines
“alternative-fuel heavy-duty vehicles” in the same manner as
in Rule 1192. The Rule allows purchases of “dual-fuel” vehi-
cles relying on both diesel and alternative fuels for certain
purposes, and operators are exempt from the Rule, inter alia,
when no alternative-fuel engine “is available commercially or
could be used.”

   Fleet Rule 1194 applies to public and private airport trans-
portation fleets, also regardless of whether the private fleets
are under public contract. The affected vehicles include taxis,
limousines, commercial shuttles, and “courtesy shuttle trans-
portation such as those provided by . . . rental agencies and
hotels.” When procuring, purchasing, or leasing vehicles, fleet
operators using passenger cars or medium-duty vehicles for
airport transportation must acquire a specified percentage of
vehicles that meet CARB’s standards for low-emission vehi-
cles. Fleet operators purchasing and leasing heavy-duty vehi-
cles must acquire alternative-fuel vehicles, defined as vehicles
“not powered by gasoline or diesel fuel.” The Rule also con-
tains various exceptions, including exemptions where no such
vehicles are available or could be used and for taxi fleets if
“[the District] . . . has not provided sufficient funding to fully
offset the purchase cost . . . less $10,000 (paid by . . . the air-
port fleet operator).”

   Fleet Rule 1196 requires public fleet operators of heavy-
duty vehicles to acquire mostly alternative-fuel or dual-fuel
vehicles when procuring, purchasing, or leasing heavy-duty
vehicles. “Alternative-fuel vehicle” is defined in the same
manner as in Rules 1186.1, 1192, and 1193. A “dual-fuel”
vehicle is defined as a vehicle “equipped with a diesel engine
that uses an alternative fuel (such as compressed or liquefied
natural gas, liquefied petroleum gas, methanol, or other
advanced technologies) in combination with diesel fuel to
enable compression ignition.” Among other exceptions, the
               ENGINE MFRS. ASS’N v. SCAQMD               10135
Rule does not apply to emergency and rescue vehicles, private
fleets with public contracts, and “[m]ilitary vehicles used for
tactical operations.” In addition, every fleet operator may
have as part of the fleet a certain number of “dedicated heavy-
duty gasoline vehicles” not meeting these standards depend-
ing on the size of the fleet.

   Each rule provides that a fleet operator must produce
records proving compliance with the Rules upon request from
the District. Each rule also contains a severability provision
stating that if any part of the rule is held invalid in a court
order, that order shall not affect the validity of the remainder
of the Rule.

   Soon after the adoption of the Fleet Rules in 2000, the
Engine Manufacturers Association (“EMA”) brought suit in
federal district court seeking declaratory and injunctive relief
from the Rules. EMA’s First Amended Complaint claimed
that the Rules were state emissions standards entirely pre-
empted by § 209(a) and § 177 of the Clean Air Act. See CAA
§ 209(a), 42 U.S.C. § 7543(a) (“No State or any political sub-
division thereof shall adopt or attempt to enforce any standard
relating to the control of emissions from new motor vehicles
or new motor vehicle engines subject to this part.”); CAA
§ 209(b), 

(providing an exception to preemption
under § 209(a) whereby the State of California can obtain a
preemption waiver from the EPA to promulgate its own emis-
sions standards); CAA § 177, 

(providing that other
states may adopt the standards promulgated by California pur-
suant to § 209(b), but that the other states’ standards must be
“identical” to California’s).

   EMA named as defendants the District, its board members,
and its executive director. The Western States Petroleum
Association intervened as a plaintiff (hereinafter, together
with EMA, “Appellants”). Various environmental organiza-
tions intervened as defendants: Coalition for Clean Air, Inc.;
Natural Resources Defense Council, Inc.; Communities for a
10136          ENGINE MFRS. ASS’N v. SCAQMD
Better Environment, Inc.; Planning and Conservation League;
and Sierra Club (hereinafter included by reference to “the
District”).

   The district court granted summary judgment to the Dis-
trict. 

(C.D. Cal. 2001). The court held
that the Rules were not preempted by § 209(a) and § 177
because they did not compel manufacturers to meet new emis-
sions standards; rather, they merely compelled fleet operators
to purchase vehicles from within classes of vehicles conform-
ing to extant California standards lawfully promulgated pur-
suant to EPA-granted waivers of § 209(a) preemption under
§ 209(b). 

(“The Fleet Rules accept as given the
existing CARB vehicle standards; they merely require fleet
operators to choose from among the least polluting of CARB-
certified, available vehicles.”); 

This court
affirmed in a published order adopting the district court’s rea-
soning. 

, 551 (9th Cir. 2002).

   The Supreme Court reversed. It rejected the argument that
the Rules “escape[d] pre-emption under § 209(a) . . . because
they address the purchase of vehicles, rather than their manu-
facture or sale.” 

, 249 (2004). The Court held
that “standard-enforcement efforts that are proscribed by
§ 209 can be directed to manufacturers or purchasers.” 

However, the Court did not decide whether the Rules
were actually preempted. See 

The Court stated that
it was “likely that at least certain aspects of the Fleet Rules
are pre-empted,” but allowed that “[i]t does not necessarily
follow . . . that the Fleet Rules are pre-empted in toto.” 

therefore remanded for further proceedings consis-
tent with its opinion.

   On remand in the district court, Appellants brought a “Mo-
tion for Order Implementing the Supreme Court’s Decision”
requesting declaratory and injunctive relief on the ground that
the Rules were preempted in their entirety. On May 6, 2005,
the district court denied Appellants’ motion. The court held
                 ENGINE MFRS. ASS’N v. SCAQMD                   10137
that Appellants had brought an unsuccessful facial challenge
because they had not carried their burden of showing that all
applications of the Fleet Rules were preempted. Specifically,
the court held that the Fleet Rules were not preempted as
applied to state and local governmental entities. According to
the court, those applications of the Rules directed state propri-
etary action and were therefore protected from Clean Air Act
preemption under the market participant doctrine. Because the
facial challenge failed, the district court declined to address
the validity of other applications of the Rules.

   Appellants then moved in the district court for a judgment
under Federal Rule of Civil Procedure 54(c). They sought a
declaratory judgment that Rules 1186.1, 1193, and 1194 were
invalid as applied to federal agencies and to private fleet oper-
ators’ purchases of new vehicles, and sought an injunction
against enforcement of those provisions.1 Appellants con-
tended that they were entitled to such a judgment based on the
District’s failure to defend those applications of the Rules in
their briefing in the district court on Appellants’ motion to
implement the Supreme Court’s decision. On September 22,
2005, the district court denied the motion, noting that since
Appellants were not the party “in whose favor [the judgment
was] rendered,” they were not entitled to a judgment under
Rule 54(c). Fed. R. Civ. P. 54(c).

   Finally, Appellants moved in the district court for entry of
final judgment under Federal Rule of Civil Procedure 58 in
accordance with the court’s orders of May 6 and September
22, 2005. On October 7, 2005, the district court entered a final
judgment dismissing Appellants’ suit with prejudice for the
reasons given in its order of May 6. Appellants timely
appealed.
  1
   The requested declaratory judgment also included relief from Fleet
Rule 1195, pertaining to school buses. However, Appellants’ First
Amended Complaint did not request relief from this Rule, and Appellants
do not argue on appeal that they are entitled to such relief.”
10138             ENGINE MFRS. ASS’N v. SCAQMD
                            II.   Discussion

   Appellants contend that the district court made two errors.
First, they contend that the district court erred in holding that
the market participant doctrine saved any applications of the
Rules from preemption. Second, they contend that, even if the
Rules are not preempted as applied to state and local govern-
ment entities, the district court erred in dismissing Appellants’
suit rather than determining which applications were pre-
empted and which were not.

  We affirm the district court’s holding that the Clean Air
Act does not preempt the Fleet Rules insofar as they direct the
procurement behavior of state and local governmental entities.
However, we agree with Appellants’ second contention and
remand to the district court for further proceedings to deter-
mine which, if any, of the Rules’ other provisions are pre-
empted.2

     A.    Preemption and the Market Participant Doctrine

   The Supremacy Clause “invalidates state laws that ‘inter-
fere with, or are contrary to,’ federal law.” Hillsborough
County v. Automated Med. Labs., Inc., 

, 712
(1985) (quoting Gibbons v. Ogden, 22 U.S. (9 Wheat.) 1, 211
(1824)); see U.S. Const., art. VI, cl. 2. “Federal preemption
   2
     We grant the District’s request for judicial notice of the transcript of
the Supreme Court’s oral argument in this case, a public report issued by
California’s Air Resources Board, and the municipal ordinance at issue in
Cardinal Towing & Auto Repair, Inc. v. City of Bedford, 

(5th Cir. 1999). The Los Angeles Taxi Industry, as amicus curiae, is alone
in opposing the request and opposes only our taking notice of the Cardinal
Towing ordinance. Municipal ordinances are proper subjects for judicial
notice. Santa Monica Food Not Bombs v. City of Santa Monica, 

, 1025 n.2 (9th Cir. 2006). The ordinance at issue in Cardinal Towing
is relevant given our adoption of that case’s analysis in Chamber of Com-
merce v. Lockyer, 

, 1084 (9th Cir. 2006) (en banc), the prin-
cipal case on which Appellants’ preemption argument relies.
               ENGINE MFRS. ASS’N v. SCAQMD                10139
occurs when: (1) Congress enacts a statute that explicitly pre-
empts state law; (2) state law actually conflicts with federal
law; or (3) federal law occupies a legislative field to such an
extent that it is reasonable to conclude that Congress left no
room for state regulation in that field.” Tocher v. City of Santa
Ana, 

, 1045-46 (9th Cir. 2000), abrogated on
other grounds by City of Columbus v. Ours Garage &
Wrecker Serv., Inc., 

, 431-34 (2002).

   “Preemption analysis ‘start[s] with the assumption that the
historic police powers of the States were not to be superseded
by the Federal Act unless that was the clear and manifest pur-
pose of Congress.’ ” City of 

(quot-
ing Medtronic, Inc. v. Lohr, 

, 485 (1996)).
“Congressional intent, therefore, is the ultimate touchstone of
preemption analysis.” 

(internal quo-
tation marks omitted). “When . . . Congress adopts a statute
that provides a reliable indication of Congressional intent
regarding preemption, the scope of federal preemption is
determined by the statute. . . . ‘Congress’ enactment of a pro-
vision defining the pre-emptive reach of a statute implies that
matters beyond that reach are not pre-empted.’ ” 

v. Liggett Group, Inc., 

, 517 (1992)).

               1.   Market Participant Doctrine

   [1] The market participant doctrine distinguishes between
a state’s role as a regulator, on the one hand, and its role as
a market participant, on the other. Actions taken by a state or
its subdivision as a market participant are generally protected
from federal preemption. The doctrine was originally devel-
oped in a series of dormant Commerce Clause cases. In
Hughes v. Alexandria Scrap Corp., 

(1976), the
Supreme Court held that Maryland did not violate the Com-
merce Clause by favoring in-state processors of scrap metal
when participating in the market for scrap metal. 

10. Subsequently, in Reeves, Inc. v. Stake, 

(1980), the Court held that South Dakota, as a seller of
10140          ENGINE MFRS. ASS’N v. SCAQMD
cement, was free to discriminate in a time of shortage by sell-
ing cement only to in-state users. The Court was moved by
“considerations of state sovereignty, the role of each State as
guardian and trustee for its people, and the long recognized
right of trader or manufacturer, engaged in an entirely private
business, freely to exercise his own independent discretion as
to parties with whom he will deal.” 

(footnotes,
citations, and internal quotation marks omitted). “Even-
handedness suggests that, when acting as proprietors, States
should similarly share existing freedoms from federal con-
straints, including the inherent limits of the Commerce
Clause.” 

The Court stated that in market participant
cases, courts undertake “a single inquiry: whether the chal-
lenged program constituted direct state participation in the
market.” 

n.7 (internal quotation marks omitted);
accord White v. Mass. Council of Constr. Employers, Inc.,

, 208 (1983) (citing Reeves’ “single inquiry” in
upholding executive order requiring all Boston construction
projects funded by city funds to be performed by work forces
of at least half city residents).

   After the development of the market participant doctrine in
these dormant Commerce Clause cases, the Supreme Court
and the lower federal courts have applied the doctrine to pro-
tect proprietary state action from preemption by various fed-
eral statutes. See, e.g., Building & Constr. Trades Council v.
Associated Builders & Contractors (“Boston Harbor”), 

, 226-27 (1993) (National Labor Relations Act);

(Federal Aviation Administra-
tion Authorization Act of 1995 (“FAAA”)); Associated Gen.
Contractors v. Metro. Water Dist., 

, 1183 (9th
Cir. 1998) (Employee Retirement Income Security Act of
1974).

  [2] In the statutory preemption context, the market partici-
pant doctrine is based on the proposition that “pre-emption
doctrines apply only to state regulation.” Boston 

. “Not all actions by state or local government enti-
                ENGINE MFRS. ASS’N v. SCAQMD                 10141
ties . . . constitute regulation, for such an entity, like a private
person, may buy and sell or own and manage property in the
marketplace.” Sprint Spectrum L.P. v. Mills, 

,
417 (2d Cir. 2002). Thus, even where a federal statute pre-
empts state regulation in an area, state action in that area is
not preempted so long as it is proprietary rather than regula-
tory. The Supreme Court has stated the rule in the negative:
“In the absence of any express or implied indication by Con-
gress that a State may not manage its own property when it
pursues its purely proprietary interests, and where analogous
private conduct would be permitted, this Court will not infer
such a restriction.” Boston 

.

   [3] In considering the scope of the market participant doc-
trine for purposes of preemption under the National Labor
Relations Act, we have adopted the Fifth Circuit’s test for dis-
tinguishing “proprietary” from “regulatory” action. In Lock-
yer, we held that state action qualifies as proprietary in either
of two circumstances. First, state action is proprietary if it “es-
sentially reflect[s] the [governmental] entity’s own interest in
its efficient procurement of needed goods and services, as
measured by comparison with the typical behavior of private
parties in similar 

(quoting
Cardinal 

). In these circumstances,
the market participant doctrine “protects comprehensive state
policies with wide application from preemption, so long as the
type of state action is essentially proprietary.” 

action is proprietary if “the narrow scope of the chal-
lenged action defeat[s] an inference that its primary goal was
to encourage a general policy rather than address a specific
proprietary problem.” 

). Thus, the doctrine also “protects narrow spending
decisions that do not necessarily reflect a state’s interest in the
efficient procurement of goods or services, but that also lack
the effect of broader social regulation.” 

with three other circuits, we have held that the
market participant doctrine’s protection of state proprietary
10142          ENGINE MFRS. ASS’N v. SCAQMD
action includes proprietary action by states’ political subdivi-
sions. Big Country Foods, Inc. v. Bd. of Educ., 

,
1178-79 (9th Cir. 1992); accord Nat’l Solid Waste Mgmt.
Ass’n v. Williams, 

, 599-600 (8th Cir. 1998);
Smith Setzer & Sons, Inc. v. S.C. Procurement Review Panel,

, 1319-20 (4th Cir. 1994); Trojan Techs., Inc. v.
Pennsylvania, 

, 911 (3d Cir. 1990); see also City
of 

(“The principle is well settled
that local governmental units are created as convenient agen-
cies for exercising such of the governmental powers of the
State as may be entrusted to them in its absolute discretion.”
(quoting Wis. Pub. Intervenor v. Mortier, 

, 607-
08 (1991)); Bldg. & Constr. Trades Dep’t, AFL-CIO v. All-
baugh, 

, 34 (D.C. Cir. 2002) (upholding under
market participant doctrine a rule prohibiting federal agencies
and entities receiving federal construction funds from requir-
ing contractors to enter, or prohibiting them from entering,
project labor agreements); 

(“[T]here is simply no
logical justification for holding that if an executive order
establishes a consistent practice regarding the use of [such
labor agreements], it is regulatory even though the only deci-
sion governed by the executive order are those that the federal
government makes as a market participant.” (internal quota-
tion marks and alteration omitted)). But see W.C.M. Window
Co. v. Bernardi, 

, 495-96 (7th Cir. 1984) (as
amended) (holding that state regulation did not fall within
market participant exception because it was not limited to the
state’s contracts, but also included those of local government
entities).

   The central question presented in this appeal is whether the
Clean Air Act preempts the Fleet Rules insofar as they apply
to state and local government entities. The answer turns on
the applicability and scope of the market participant doctrine
as it relates to preemption under the Act. Because the market
participant doctrine is not a wholly freestanding doctrine, but
rather a presumption about congressional intent, the doctrine
may have a different scope under different federal statutes. It
               ENGINE MFRS. ASS’N v. SCAQMD                10143
is possible that some aspects of the doctrine have a constitu-
tional dimension, protecting certain sovereign actions of the
states from unconstitutional interference by the federal gov-
ernment. Cf. Nat’l League of Cities v. Usery, 

,
841-44, 854-55 (1976), overruled by Garcia v. San Antonio
Metro. Transit Auth., 

, 557 (1985). But we need
not pursue the constitutional issue here, for — whatever the
precise scope of the market participant doctrine under the
Clean Air Act — we are presented with a statutory question
under the Act rather than a constitutional question under the
Tenth Amendment.

 2.   Market Participant Doctrine Under the Clean Air Act

   The district court’s decision in this case appears to be the
first of any court to analyze the market participant doctrine
under the federal Clean Air Act. Because congressional intent
is the key to preemption analysis, we must consider whether
the Act contains “any express or implied indication by Con-
gress” that the presumption embodied by the market partici-
pant doctrine should not apply to preemption under the Act.
Boston 

.

   The Clean Air Act largely preserves the traditional role of
the states in preventing air pollution. Cf. Exxon Mobil Corp.
v. EPA, 

, 1255 (9th Cir. 2000) (“Air pollution
prevention falls under the broad police powers of the states,
which include the power to protect the health of citizens in the
state.”). As we have previously noted, “[t]he overriding pur-
pose of the Clean Air Act is to force the states to do their job
in regulating air pollution effectively so as to achieve baseline
air quality standards, the [national ambient air quality stan-
dards (‘NAAQS’)].” 

see also 42 U.S.C.
§ 7408(a). Indeed, the Act’s congressional findings state that
“air pollution prevention (that is, the reduction or elimination,
through any measures, of the amount of pollutants produced
or created at the source) and air pollution control at its source
10144          ENGINE MFRS. ASS’N v. SCAQMD
is the primary responsibility of States and local governments.”
42 U.S.C. § 7401(a)(3).

   States discharge their primary responsibility for attaining
and maintaining the NAAQS through their state implementa-
tion plans (“SIPs”). See 

The section of the Act
concerning SIPs reaffirms the primary responsibility of the
states: “Each State shall have the primary responsibility for
assuring air quality within the entire geographic area compris-
ing such State by submitting an implementation plan for such
State which will specify the manner in which national primary
and secondary ambient air quality standards will be achieved
and maintained within each air quality control region in such
State.” 

   The Act also contains a provision titled “Retention of State
authority.” 

That section provides that, with certain
exceptions, “nothing in this chapter shall preclude or deny the
right of any State or political subdivision thereof to adopt or
enforce (1) any standard or limitation respecting emissions of
air pollutants or (2) any requirement respecting control or
abatement of air pollution.” 

and we agree, that the market partici-
pation doctrine applies to preemption under § 209(a) and
§ 177 of the Clean Air Act. Neither of these two provisions
indicates that Congress intended to extend the provisions’
reach to preempt state proprietary action.

  Section 209(a) provides, in its entirety:

    No State or any political subdivision thereof shall
    adopt or attempt to enforce any standard relating to
    the control of emissions from new motor vehicles or
    new motor vehicle engines subject to this part. No
    State shall require certification, inspection, or any
    other approval relating to the control of emissions
    from any new motor vehicle or new motor vehicle
                 ENGINE MFRS. ASS’N v. SCAQMD                   10145
      engine as condition precedent to the initial retail
      sale, titling (if any), or registration of such motor
      vehicle, motor vehicle engine, or equipment.

42 U.S.C. § 7543(a).

   [5] Section 209(a) prevents a state (absent a waiver granted
to the State of California under § 209(b)) from imposing
emissions standards more stringent than or otherwise different
from the federal standards. However, the section contains
nothing to indicate a congressional intent to bar states from
choosing to use their own money to acquire or use vehicles
that exceed the federal standards. Inferring such a limit on
state proprietary action would run afoul of the presumption
articulated in Boston 

. It would
also run afoul of the Clean Air Act’s express reservation to
the states of primary authority over and responsibility for con-
trolling air pollution.

    [6] Section 177 is a corollary to § 209(b) of the Act. Sec-
tion 209(b) provides that the EPA “shall” grant the State of
California a waiver from § 209(a) preemption to adopt and
enforce its own emission standards, provided that California
has determined that the standards are, “in the aggregate, at
least as protective of public health and welfare as applicable
Federal standards.” 

see also Motor & Equip.
Mfrs. Ass’n, Inc. v. EPA, 

, 1108-11 (D.C. Cir.
1979) (as amended) (discussing the history and purpose of
§ 209(b)); Am. Auto. Mfrs. Ass’n v. Cahill, 

, 198-
99 (2d Cir. 1998) (describing the standards California has pro-
mulgated under § 209(b) waivers, codified at Cal. Code Regs.
tit. 13, §§ 1900 et seq.).3 Section 177 provides that states other
than California may require that vehicles sold in their state
comply with standards that are “identical to the California
standards for which a waiver has been granted [under
  3
   There is no contention that California has obtained a waiver for the
Fleet Rules under § 209(b).
10146          ENGINE MFRS. ASS’N v. SCAQMD
§ 209(b)] for such model year.” 42 U.S.C. § 7507. Like
§ 209(a), § 177 contains no language impliedly or expressly
limiting states’ proprietary action, and we decline to infer
such a limit for the reasons just stated regarding § 209(a).

   An amicus, the Los Angeles Taxi Industry (“LATI”),
argues that the market participation doctrine does not apply to
preemption analysis under any section of the Clean Air Act.
Another amicus, the American Automotive Leasing Associa-
tion (“AALA”), argues that § 246 of the Act preempts the
Fleet Rules even as they apply to state and local governments.
“Generally, we do not consider on appeal an issue raised only
by an amicus.” Chaker v. Crogan, 

, 1220 (9th
Cir. 2005) (quoting Swan v. Peterson, 

, 1383 (9th
Cir. 1993)). However, because the central question in this
case is the applicability and scope of the market participant
exception under the Clean Air Act, and because there are
ready answers, we respond to LATI’s and AALA’s argu-
ments.

   LATI argues that the market participant doctrine is not
applicable to preemption analysis under the Clean Air Act
based on our suggestion in dictum in Hydrostorage, Inc. v. N.
Cal. Boilermakers Local Joint Apprenticeship Comm., 

, 730 (9th Cir. 1989), that the market participant doc-
trine does not exist outside the dormant Commerce Clause
context. We have since acknowledged, however, that our dic-
tum in Hydrostorage was not the product of “deep consider-
ation,” given that in Hydrostorage we held that the action was
regulatory rather than proprietary. Associated Gen. Contrac-

. Moreover, as we have also noted, our
dictum was abrogated by Boston Harbor, which applied the
market participant doctrine to preemption under the NRLA.

Harbor). LATI asserts that Boston Harbor
is distinguishable because it “did not involve express preemp-
tion.” However, Boston Harbor does not support a distinction
between express and other forms of preemption. Boston Har-
bor holds that the Court will not “infer” preemption of propri-
               ENGINE MFRS. ASS’N v. SCAQMD               10147
etary action unless Congress “indicat[es] . . . that a State may
not manage its own property when it pursues its purely propri-
etary 

. LATI does not point us to
any such indication by Congress in the Clean Air Act. See
also 

(holding that market participant
doctrine protected portion of a city ordinance from express
preemption by 49 U.S.C. § 14501(c)).

   [7] AALA argues that § 246 of the Clean Air Act, 42
U.S.C. § 7586, precludes application of the market participant
doctrine. Section 246 requires that states with certain nonat-
tainment areas adopt specified rules for “centrally fueled
fleets” as part of their SIPs. Section 246 does not mention
government-owned fleets, but under chapter-wide definitions
“covered fleets” include both private and government-owned
fleets. See 42 U.S.C. §§ 7581(5), 7602(e). AALA does not
argue that adhering to the Fleet Rules in procuring vehicles
would cause state and local entities to fail to meet SIP-
imposed fleet standards. Rather, AALA argues that the Rules
conflict with § 246 because, under SIPs promulgated by a
state pursuant to § 246, a fleet operator “shall” have “the
choice of clean-fuel vehicles and clean alternative fuels,” 

whereas the Rules preclude fleet operators from
making that choice. This conflict between § 246 and the Fleet
Rules might support a holding that the Rules are preempted
as applied to private fleet operators. However, it does not sup-
port a holding that the § 209(a) and § 177 preempt the Rules
as applied to state and local governments acting in their
capacities as fleet operators. The requirement that a state’s
SIP give fleet operators a choice among fuels and vehicles is
entirely consistent with the state’s own ability to choose to
purchase particular fuels and vehicles in its proprietary capac-
ity as a fleet operator.

   [8] We therefore conclude that § 209(a), § 177, and § 246
of the Clean Air Act do not contain any express or implied
indication of congressional intent that they should extend to
state proprietary action.
10148            ENGINE MFRS. ASS’N v. SCAQMD
          3.   Scope and Application of the Doctrine

   Appellants contend that even though the market participant
doctrine protects a state’s proprietary action from Clean Air
Act preemption, the doctrine does not protect the Fleet Rules.
According to Appellants, all of the Fleet Rules’ provisions
constitute regulatory rather than proprietary action under
either of Lockyer’s two categories of state proprietary action.4

   As an initial matter, we note that our analysis in Lockyer
addressed the market participant doctrine in the context of
preemption by the National Labor Relations Act (“NLRA”).
While the Clean Air Act expressly reserves to the states their
traditional police powers in regulating pollution except in a
few limited areas of express preemption, the NLRA preempts
broad swaths of state labor regulation. Compare Exxon 

, with Boston 

(describing the NLRA preemption doctrines “prohibit[ing
state] regulation even of activities that the NLRA only argu-
ably protects or prohibits” and “of areas that [Congress] left
to be controlled by the free play of economic forces” (internal
quotation marks omitted; emphasis in original)). Due regard
for congressional intent requires that we not mechanically
apply our market participant analysis in Lockyer to preemp-
tion analyses of federal statutes other than the NLRA.
Depending on Congress’s intent, another statute might require
us to employ a definition of protected state “proprietary
action” different from the two definitions adopted in Lockyer
for purposes of preemption under the NLRA.

  Nevertheless, in the case before us, we need not consider
  4
   Appellants’ arguments on this issue conflict with their counsel’s con-
cessions at oral argument before the Supreme Court. Appellants’ counsel
conceded — as did the Solicitor General (as amicus curiae in support of
Appellants) — that the Rules were not preempted insofar as they applied
only to state and local government purchases. Transcript of Oral Argu-
ment at 6-8, 20-25, 28, 

(2004) (No. 02-1343).
                ENGINE MFRS. ASS’N v. SCAQMD                10149
other possible definitions of “proprietary action,” for the Fleet
Rule provisions governing purchasing, procuring, leasing, and
contracting for the use of vehicles by state and local govern-
mental entities fall squarely within Lockyer’s first category of
state proprietary action. That is, these provisions “essentially
reflect the [state] entity’s own interest in its efficient procure-
ment of needed goods and services, as measured by compari-
son with the typical behavior of private parties in similar
circumstances.” 

(quoting Cardinal

).

   As described in greater detail above, Fleet Rule 1186.1
directs state and local government entities to meet certain
criteria when purchasing or leasing street sweepers and, if fea-
sible to do so, when contracting for use of street sweepers;
Rule 1191 directs the same state entities to choose vehicles
that meet certain criteria when procuring or leasing cars, light-
duty trucks, and medium-duty vehicles; Rule 1192 directs
them to meet certain criteria when procuring or leasing vehi-
cles for public transit fleets; Rule 1193 directs them to meet
certain criteria when procuring or leasing solid waste collec-
tion vehicles; Rule 1194 directs them to meet certain criteria
when procuring, purchasing, or leasing vehicles for transpor-
tation providing ground access to airports; and Rule 1196
directs them to meet certain criteria when procuring, purchas-
ing, or leasing heavy-duty vehicles.

   We conclude that these provisions directing state and local
governmental entities to purchase, procure, lease, or contract
for use of vehicles meeting specified air pollution criteria con-
stitute direct state participation in the market. We so conclude
even though not only the state, but also some of its political
subdivisions, are directed to take these actions. See Big Coun-
try 

(“A state should not be penalized
for exercising its power through smaller, localized units; local
control fosters both administrative efficiency and democratic
governance.”).
10150           ENGINE MFRS. ASS’N v. SCAQMD
   [9] Appellants object to this conclusion on three grounds.
First, they contend that the Fleet Rules are not concerned with
“efficient procurement” within the meaning of 

, because the Rules’ purpose is to reduce air pol-
lution. Appellants point to the legislative history of the statute
pursuant to which the Rules were adopted, California Health
& Safety Code § 40447.5, which makes this purpose clear.
We do not regard this purpose as fatal to the Rules. That a
state or local governmental entity may have policy goals that
it seeks to further through its participation in the market does
not preclude the doctrine’s application, so long as the action
in question is the state’s own market participation. See, e.g.,
Alexandria 

(“Maryland entered the
market for the purpose, agreed by all to be commendable as
well as legitimate, of protecting the State’s environment. As
the means of furthering this purpose, it elected the payment
of state funds in the form of bounties to encourage the
removal of automobile hulks from Maryland streets and junk-
yards.”); Boston 

, 232 (upholding
against an NLRA preemption challenge a requirement that all
contractors on a public construction project adhere to a pre-
hire labor agreement and noting that the Court had not held
in Wis. Dep’t of Indus., Labor & Human Relations v. Gould
Inc., 

(1986), that purchasing decisions “may
never be influenced by labor considerations”); Big Country

(upholding Alaska statute requiring
school districts to pay up to 7 percent more for milk in order
to purchase in-state milk rather than out-of-state milk); see
also N. Ill. Chapter of Associated Builders & Contractors,
Inc. v. Lavin, 

, 1007 (7th Cir. 2005) (“Federal
preemption doctrine evaluates what legislation does, not why
legislators voted for it or what political coalition led to its
enactment.”); 

in Boston Harbor, “Boston
wanted to clean up its harbor, but there can be little doubt that
it also wanted to shower benefits on workers who were the
incumbents’ political supporters”); cf. 

(holding that Wisconsin law prohibiting state procurement
agents from purchasing products from repeat NLRA violators
               ENGINE MFRS. ASS’N v. SCAQMD               10151
was not protected by the market participant doctrine because
the statute “function[ed] unambiguously as a supplemental
sanction for violations of the NLRA” rather than as state pro-
prietary action); 

-85 (holding state
action not proprietary where statute placed spending restric-
tions related to labor organizing on all private employers
receiving more than $10,000 in state funds).

   In arguing that the Fleet Rules are not concerned with “effi-
cient procurement” by state and local governments within the
meaning of Lockyer, Appellants read the word “efficient” too
narrowly. “Efficient” does not merely mean “cheap.” In con-
text, “efficient procurement” means procurement that serves
the state’s purposes — which may include purposes other
than saving money — just as private entities serve their pur-
poses by taking into account factors other than price in their
procurement decisions. See Boston 

(“To the extent that a private purchaser may choose a contrac-
tor based upon that contractor’s willingness to enter into a
prehire agreement, a public entity as purchaser should be per-
mitted to do the same.”); see also 

(comparing
state’s labor agreement to private construction firms’ agree-
ments).

   [10] Tellingly, Appellants do not argue that the Fleet Rules
fall outside Lockyer’s first definition of state proprietary
action on the ground that private fleet operators do not take
air pollution concerns into account when making their pro-
curement decisions. Such an argument would be contradicted
by evidence presented in this case that two prominent private
fleet owners, FedEx and UPS, have, for their own purposes,
adopted programs to introduce less-polluting vehicles into
their fleets. There is therefore no basis for concluding that
purchasing less-polluting vehicles is not a purpose that a state
may pursue as a market participant.

   Second, Appellants contend that the Fleet Rules do not con-
stitute proprietary action because they “do not control the dis-
10152          ENGINE MFRS. ASS’N v. SCAQMD
position of any state funds or property.” That is, the Rules
direct not how the State of California shall spend its own
money, but rather how political subdivisions of the state shall
spend their money. This argument is largely foreclosed by Big
Country Foods, in which we held that the market participant
doctrine saved from a dormant Commerce Clause challenge
an Alaska statute that directed the purchase of milk by local
school 

. There, we rejected an
analogous argument that the market participant doctrine did
not apply because, although Alaskan school districts entered
into the milk contracts, federal funds ultimately paid for the
milk: “Federal funds provide the wherewithal to make the
milk purchases, but it is Alaska that is the direct participant
in the market. Accordingly, the market participant exception
applies.” 

In so holding, we rejected what we saw
as “strong public policy arguments to the contrary,” because
such arguments “extend the debate beyond the ‘single
inquiry’ the Supreme Court demands: ‘whether the challenged
program constituted direct state participation in the market.’ ”

marks omitted) (quoting 

(quoting 

n.7)); see also
Cardinal 

(holding doctrine protected
towing ordinance from FAAA preemption where ordinance
governed city contracts for “nonconsensual” towing services
ultimately paid for by the people whose cars were towed).

   [11] Like Alaska’s milk ordinance, the Fleet Rules consti-
tute direct state participation in the market. The Rules are a
state directive determining which vehicles the state and its
political subdivisions will procure. While it is true that the
local governments may spend their own money rather than the
state’s in complying with the Rules, this fact is not inconsis-
tent with the doctrine. Appellants do not contend that the
State of California lacks the power under state law to compel
its political subdivisions to purchase particular vehicles and to
spend local funds in so doing. We cannot discern any reason
why the market participant doctrine should not apply merely
because the state, which has the legal right under state law to
                   ENGINE MFRS. ASS’N v. SCAQMD                       10153
direct the actions of local governments, directs the expendi-
ture of local rather than state funds.5

   Third, Appellants contend that the Fleet Rules are regula-
tory rather than proprietary because they are enforceable by
criminal sanctions and fines. However, Appellants do not
explain why such enforcement provisions preclude the appli-
cation of the market participant doctrine. They assert in their
brief only that in Lockyer we “emphasized the enforcement
provisions of the statute as reinforcing [its] regulatory charac-
ter.” In fact, we merely mentioned the existence of enforce-
ment 

, and did so in the context
of a statute that quite plainly functioned as regulatory rather
than proprietary action, irrespective of any means chosen to
enforce it. Here, by contrast, the provisions of the Fleet Rules
directed to the procurement decisions of the state and local
governments clearly constitute proprietary action within the
meaning of the market participant doctrine.

  [12] We do not believe that the enforcement provisions
have the effect of transforming the Rules from proprietary to
regulatory action. It is unclear whether the criminal sanctions
and fines provided in the Fleet Rules are intended to be, or
  5
   During oral argument in the Supreme Court, Appellants’ counsel
appears to have conceded this point, arguing only that the state could not
control criteria for fleet purchases by entities other than local govern-
ments:
      Q:   And could [the state] also do that for all their governmental
           subdivisions? The State of Nebraska says that the State and
           all of its subdivisions will have some very strict standards —
      A:   I agree with the . . . way that the Chief Justice put it, that
           that’s their own purchasing decisions, and it’s a matter of
           State law as to whether they can — but that is not what this
           case is about. This case is about whether the South Coast
           district can impose those standards, including Federal Gov-
           ernment vehicles, postal vehicles, FBI vehicles, private vehi-
           cles that go to the airports and so forth.
Transcript of Oral Argument at 25, 

(2004) (No. 02-1343).
10154          ENGINE MFRS. ASS’N v. SCAQMD
are, enforceable against government entities, as distinct from
private parties. But even if they are so enforceable, we do not
see how action by a state or local government that is propri-
etary when enforced by one mechanism loses its proprietary
character when enforced by some other mechanism.

   As part of their argument that the Rules are regulatory,
Appellants contend that protecting the Fleet Rules from pre-
emption under the market participant doctrine “would seri-
ously undermine the uniformity contemplated by § 209(a).”
They assert that “purchases by government entities . . . in the
aggregate no doubt represent a very substantial segment of the
market.” However, Appellants cite no evidence from the
record in support of an argument based on the market share
of the state and local governments, and we see no such evi-
dence. Nor do Appellants cite any case in which a court has
held that a state’s market power was so great as to preclude
the application of the market participant doctrine. Cf. 

(holding that South Dakota, as a seller of
cement, was free to discriminate in a time of shortage by sell-
ing cement only to in-state users). Congress is of course free
to amend § 209(a) to eliminate the market participant doc-
trine’s presumption of non-preemption if Congress finds that
state proprietary action has undermined § 209(a)’s purpose.

   [13] For the foregoing reasons, we hold that the Fleet Rule
provisions directing state and local governments to purchase,
procure, lease, and contract for use of vehicles meeting cer-
tain criteria fall within Lockyer’s first category of proprietary
state action because they “essentially reflect [California’s]
own interest in its efficient procurement of needed goods and
services.” 

(quoting Cardinal Tow-

). The market participant doctrine there-
fore saves those provisions of the Fleet Rules from
preemption by the Clean Air Act, and we need not consider
whether the Rules also fall within Lockyer’s second category
of state proprietary action. See 

proprietary
“narrow spending decisions that do not necessarily reflect a
               ENGINE MFRS. ASS’N v. SCAQMD               10155
state’s interest in the efficient procurement of goods or ser-
vices, but that also lack the effect of broader social regula-
tion”).

          B.   Other Provisions of the Fleet Rules

   Appellants contend that the district court erred in refusing
to consider whether the Clean Air Act preempts the other pro-
visions of the Fleet Rules that are not protected by the market
participant doctrine.

   The Supreme Court stated in United States v. Salerno, 

(1987) that “[a] facial challenge to a legislative Act
is, of course, the most difficult challenge to mount success-
fully, since the challenger must establish that no set of cir-
cumstances exists under which the Act would be valid.” 

cf. Hotel & Motel Ass’n of Oakland v. City of Oakland,

, 971-72 (9th Cir. 2003) (following this rule
from Salerno but noting that a plurality of the Supreme Court
deemed it dictum and questioned its viability in City of Chi-
cago v. Morales, 

, 55 n.22 (1999)). We agree with
the district court’s conclusion that Appellants brought a facial
challenge to the Fleet Rules. Appellants’ First Amended
Complaint requested declaratory and injunctive relief on the
ground that the Rules were preempted in their entirety by the
Clean Air Act. Nothing in that complaint indicated that
Appellants were bringing an as-applied challenge; the com-
plaint sought invalidation of the Rules in toto without refer-
ence to any particular application.

  At oral argument before the Supreme Court, counsel for
Appellants stated that they had brought “a facial challenge”
and were “claiming total preemption.” Transcript of Oral
Argument at 4, 

(2004) (No. 02-1343). On
remand, Appellants again reiterated their contention that the
Fleet Rules were wholly preempted in their “Motion for Order
Implementing the Supreme Court’s Decision.” The motion
requested (1) a declaration that the Fleet Rules “are pre-
10156           ENGINE MFRS. ASS’N v. SCAQMD
empted by Section 209(a) . . . and are invalid in their entirety”
and (2) an injunction preventing the District “from enforcing
or attempting to enforce any of the provisions of any of the
Fleet Rules.”

   [14] Given Appellants’ failure on remand to make a more
fine-grained preemption argument, we have sympathy for the
decision of the district court that, because certain Fleet Rule
provisions were protected by the market participant doctrine,
Appellants’ facial challenge entirely failed under Salerno.
Nevertheless, we conclude that the district court, after holding
that the market participant doctrine protects from preemption
the provisions governing procurement decisions by the state
and local governments, should have gone on to address
whether the remaining provisions were preempted. Where a
plaintiff challenges an enactment as prima facie invalid,
Salerno requires the plaintiff to show that there can be no
valid application of a particular challenged provision. How-
ever, Salerno does not require a plaintiff to show that every
provision within a particular multifaceted enactment is
invalid. “When a statute contains unobjectionable provisions
that are separable from those found to be unconstitutional, a
court reviewing the statute should maintain the statute in so
far as it is valid.” Nat’l Collegiate Athletic Ass’n v. Miller, 

, 640 (9th Cir. 1993) (citing Alaska Airlines, Inc. v.
Brock, 

, 684 (1987)). In other words, some of the
provisions might be facially invalid, and might not.

   [15] Each Fleet Rule contains multiple provisions, placing
restrictions on specific lists of public or private entities. Those
provisions within the Rules that constitute state proprietary
action are valid provisions, not valid applications of a single,
unseverable provision. Cf. 

(holding
that one provision of towing ordinance was preempted, that
another provision escaped preemption under the market par-
ticipant exception, and that “there [was] no need to strike
down the [ordinance] in its entirety” due to a severability
clause). We therefore remand to the district court for it to
                  ENGINE MFRS. ASS’N v. SCAQMD                       10157
decide in the first instance whether the remaining provisions
of the Fleet Rules are preempted by the Clean Air Act.6

                               Conclusion

  We affirm the district court’s holding that, under the market
participant doctrine, the Clean Air Act does not preempt those
provisions of the Fleet Rules directing state and local govern-
mental entities’ purchasing, procuring, leasing, and contract-
ing decisions. We vacate the district court’s dismissal of
Appellants’ claims with the respect to the Fleet Rules’ other
provisions. We also grant the District’s request for judicial
notice. We remand for further proceedings not inconsistent
with this opinion.

 AFFIRMED in part; VACATED in part; and
REMANDED. Each side shall bear its own costs on appeal.




  6
    We note that the record before us contains an “Advisory Notice to
Fleets Subject to SCAQMD Fleet Vehicle Rules 1186.1, 1191, 1192,
1193, 1194, 1195, and 1196,” dated July 20, 2005. The Advisory Notice
states that, following the district court’s May 6, 2005 order, the Fleet
Rules would be enforced only “as they apply to state and local public enti-
ties” or “private entities under contract to state or local public entities,”
and would not be “affirmatively enforce[d]” as applied “to private entities
that are not under contract to state or local public entities” or to “federal
public entities.” We cannot conclude, on the basis of this Advisory Notice
alone, that Appellants’ case is moot. Cf. City of Mesquite v. Aladdin’s
Castle, Inc., 

, 289 (1982) (“Mere voluntary cessation of
allegedly illegal conduct does not moot a case . . . .” (internal quotation
marks omitted)). We leave it to the district court to determine whether any
other events not reflected in the record before us have rendered the case
moot.