FOR PUBLICATION
  UNITED STATES COURT OF APPEALS
       FOR THE NINTH CIRCUIT

ROBERT MILLER,                            
                   Plaintiff-Appellant,          No. 06-56468
                   v.
                                                  D.C. No.
                                               CV-01-00434-SGL
THE CALIFORNIA     SPEEDWAY
CORPORATION,                                      OPINION
              Defendant-Appellee.
                                          
         Appeal from the United States District Court
             for the Central District of California
         Stephen G. Larson, District Judge, Presiding

                    Argued and Submitted
             April 11, 2008—Pasadena, California

                       Filed August 8, 2008

       Before: William C. Canby, Jr. and Jay S. Bybee,
       Circuit Judges, and Roger Hunt,* District Judge.

                    Opinion by Judge Bybee




  *The Honorable Roger Hunt, Chief United States District Judge for the
District of Nevada, sitting by designation.

                                10185
10190          MILLER v. CALIFORNIA SPEEDWAY
                         COUNSEL

Mark D. Potter and Russell C. Handy, Center for Disability
Access, LLP, San Marcos, California, for the plaintiff-
appellant.

John S. Lowenthal and Bryan R. Reid, Lewis Brisbois Bis-
gaard & Smith, LLP, San Bernardino, California, for the
defendant-appellee.

Karen L. Stevens, United States Department of Justice, Civil
Rights Division, Appellate Section, Washington, D.C., for the
Amicus United States.

Carolyn R. Young, Chapman University School of Law,
Orange, California; Paula D. Pearlman, Disability Rights
Legal Center, Los Angeles, California, for the Amicus San
Diego Polio Survivors.


                         OPINION

BYBEE, Circuit Judge:

   Appellant Robert Miller is a big fan of NASCAR, attending
from three to six events a year at the California Speedway in
Fontana. He also happens to be a quadriplegic who uses an
electric wheelchair. When the fans immediately in front of
Miller stand during the most exciting parts of the race, they
block his view of the action.

   Appellee California Speedway Corporation (“Speedway”)
opened the California Speedway in 1997. The track and sta-
dium, which sponsors NASCAR events, has two areas for
wheelchairs in the grandstands; the cheaper seats are located
at the bottom of the stadium, and the more expensive seats are
located near the top. Miller always purchases tickets for the
top row.
                MILLER v. CALIFORNIA SPEEDWAY              10191
   Miller brought this suit, claiming that Speedway has vio-
lated Title III of the Americans with Disabilities Act
(“ADA”), 42 U.S.C. § 12181 et seq., and a Department of
Justice regulation requiring that wheelchair areas “provide
people with physical disabilities . . . lines of sight comparable
to those for members of the general public.” 28 C.F.R. pt. 36,
App. A, § 4.33.3 (italics omitted). The district court granted
Speedway’s motion for summary judgment on the ground that
the DOJ regulation does not address the question of lines of
sight over standing spectators. Miller v. California Speedway
Corp., 

, 1204 (C.D. Cal. 2006).

   As the district court noted, two federal courts of appeals
and two federal district courts have addressed this precise
question and have reached opposite conclusions. The Third
Circuit and the District of Oregon concluded that the DOJ’s
regulation does not require lines of sight over standing specta-
tors. Caruso v. Blockbuster-Sony Music Entm’t Centre at the
Waterfront, 

, 736-37 (3rd Cir. 1999); Indep. Liv-
ing Res. v. Oregon Arena Corp., 

, 742-43 (D.
Oregon 1997). By contrast, the D.C. Circuit and the District
of Minnesota found that the DOJ’s regulation does require
lines of sight over standing spectators. Paralyzed Veterans of
America v. D.C. Arena L.P., 

, 587 (D.C. Cir.
1997); United States v. Ellerbe Becket, Inc., 

, 1269 (D. Minn. 1997). We agree with the D.C. Circuit
and reverse the judgment of the district court.

         I.   FACTS AND PROCEEDINGS BELOW

A.     The Regulatory Scheme

  1.    The Americans With Disabilities Act

   [1] Title III of the ADA prohibits discrimination against
any individual “on the basis of disability in the full and equal
enjoyment of the goods, services, facilities, privileges, advan-
tages, or accommodations of any place of public accommoda-
10192            MILLER v. CALIFORNIA SPEEDWAY
tion.” 42 U.S.C. § 12182(a). Discrimination includes “a
failure to remove architectural barriers” or “where . . .
removal of a barrier . . . is not readily achievable, a failure to
make such goods, services, facilities, privileges, advantages,
or accommodations available through alternative methods.”
42 U.S.C. § 12182(b)(2)(A)(iv), (v). The ADA further
requires that newly constructed facilities be “readily accessi-
ble to and usable by individuals with disabilities.” 42 U.S.C.
§ 12183(a)(1). The ADA directs the Attorney General to
“issue regulations . . . that include standards applicable to
facilities” covered by Title III and to provide “appropriate
technical assistance manuals to individuals or entities with
rights or duties” under Title III. 42 U.S.C. §§ 12186(b),
12206(c)(3). Congress instructed the Attorney General to
issue regulations within one year of the enactment of the
ADA. 42 U.S.C. § 12186(b).

   [2] The process by which the Attorney General promul-
gates his regulations has an unusual twist. Congress mandated
that the Attorney General’s regulations “be consistent with the
minimum guidelines and requirements issued by the Architec-
tural and Transportation Barriers Compliance Board,” 42
U.S.C. § 12186(c), commonly referred to as the “Access
Board.” The Access Board is an independent federal agency
comprised of twenty-five persons—thirteen presidentially-
appointed individuals and representatives from twelve federal
agencies, including the DOJ. 29 U.S.C. § 792(a)(1). The
Board is directed to establish “minimum guidelines and
requirements for the standards issued” under Title III of the
ADA, 29 U.S.C. § 792(b)(3)(B), and to “develop advisory
information for, and provide appropriate technical assistance
to, individuals or entities with rights or duties under regula-
tions prescribed” under Title III, 29 U.S.C. § 792(b)(2). In
sum, the Board establishes “minimum guidelines” for Title
III, but the DOJ promulgates its own regulations, which must
be consistent with—but not necessarily identical to—the
Board’s guidelines. Congress instructed the Board to issue its
                   MILLER v. CALIFORNIA SPEEDWAY             10193
guidelines within nine months of the enactment of the ADA.
42 U.S.C. § 12204(a).

  2.     The Access Board Guidelines and DOJ Standards

   In January 1991, six months after the enactment of the
ADA, the Access Board published its first proposed ADA
Accessibility Guidelines, known as the ADAAG. 56 Fed.
Reg. 2296 (1991). Initially, the provision discussing assembly
areas provided:

       4.33.3 Placement of Wheelchair Locations. Wheel-
       chair areas shall be an integral part of any fixed seat-
       ing plan and shall be dispersed throughout the
       seating area. They shall . . . be located to provide
       lines of sight comparable to those for all viewing
       areas.

56 Fed. Reg. at 2380. In commentary on its proposed rules,
the Access Board noted that the “lines of sight” requirement

       appears to be adequate for theaters and concert halls,
       but may not suffice in sports areas or race tracks
       where the audience frequently stands throughout a
       large portion of the game or event. In alterations of
       existing sports arenas, accessible spaces are fre-
       quently provided at the lower part of a seating tier
       projecting out above a lower seating tier or are built
       out over existing seats at the top of a tier providing
       a great differential in height. These solutions can
       work in newly constructed sports arenas as well, if
       sight lines relative to standing patrons are considered
       at the time of initial design. The Board seeks com-
       ments on whether the full lines of sight over standing
       spectators in sports arenas and other similar assem-
       bly areas should be required.

56 Fed. Reg. at 2314.
10194           MILLER v. CALIFORNIA SPEEDWAY
   One month later, in February 1991, the DOJ published its
own Notice of Proposed Rulemaking. 56 Fed. Reg. 7452
(1991). With respect to the standards for new construction and
alterations, the proposed rules stated that the standards would
be published as Appendix A, and that Appendix A would be
the ADAAG proposed by the Access Board in its January
1991 notice of proposed rulemaking, together “with any
amendments made by the [Access Board] during its rulemak-
ing process.” 56 Fed. Reg. at 7478, 7492. “The Department
proposes to adopt these guidelines as the accessibility stan-
dard applicable under this rule.” 56 Fed. Reg. at 7478-79. The
DOJ requested that any comments on the Access Board’s
notice of proposed rulemaking be sent to the Access Board.
56 Fed. Reg. at 7479.

   In July 1991, the Access Board published its final
ADAAG. 56 Fed. Reg. 35,408 (1991). Section 4.33.3 was
modified to read, “Wheelchair areas shall be an integral part
of any fixed seating plan and shall be provided so as to pro-
vide people with physical disabilities a choice of admission
prices and lines of sight comparable to those for members of
the general public.” 56 Fed. Reg. at 35,514 (italics omitted).
The Board addressed the problem of “lines of sight over
standing spectators in sports arenas and other similar assem-
bly areas” and noted that “[m]any commenters also recom-
mended that lines of sight should be provided over standing
spectators.” 56 Fed. Reg. at 35,440. To this, the Access Board
simply stated that “the issue of lines of sight over standing
spectators will be addressed in guidelines for recreational
facilities,” 

Access Board, evidently, had not
proposed.

   The very same day that the Access Board finalized its
guidelines, the DOJ issued its final Title III regulations. 56
Fed. Reg. 35,544 (1991). As the DOJ had previously
announced, it “adopt[ed] the ADAAG as the accessibility
standard applicable under this rule.” 56 Fed. Reg. at 35,585.
The DOJ incorporated the ADAAG—including § 4.33.3—
                  MILLER v. CALIFORNIA SPEEDWAY            10195
verbatim in Appendix A. See 28 C.F.R. 36.406 & App. A.
The commentary accompanying the regulations stated that the
“[DOJ] put the public on notice, through the proposed rule, of
its intention to adopt the proposed ADAAG, with any changes
made by the Board, as the accessibility standards.” 56 Fed.
Reg. at 35,586. The DOJ further indicated that “comments on
the Department’s proposed rule . . . have been addressed ade-
quately in the final ADAAG. Largely in response to com-
ments, the Board made numerous changes from its proposal.”

did not expressly address lines of sight.

  3.     The DOJ’s Technical Assistance Manual

   Title III’s new construction provisions, including § 4.33.3,
became effective in January 1993. That same year, pursuant
to Title III’s directive to provide technical assistance to cov-
ered entities, the DOJ published a Technical Assistance Man-
ual (“TAM”). See 42 U.S.C. § 12206(a), (c)(2)(C). The 1993
TAM was silent on § 4.33.3. The 1994 published supplement
to the TAM, however, provided an interpretation for § 4.33.3
that was more aggressive than the Access Board’s commen-
tary:

       In addition to requiring companion seating and dis-
       persion of wheelchair locations, ADAAG requires
       that wheelchair locations provide people with dis-
       abilities lines of sight comparable to those for mem-
       bers of the general public. Thus, in assembly areas
       where spectators can be expected to stand during the
       event or show being viewed, the wheelchair loca-
       tions must provide lines of sight over spectators who
       stand. This can be accomplished in many ways,
       including placing wheelchair locations at the front of
       a seating section, or by providing sufficient addi-
       tional elevation for wheelchair locations placed at
       the rear of seating sections to allow those spectators
       to see over the spectators who stand in front of them.
10196            MILLER v. CALIFORNIA SPEEDWAY
TAM § III-7.5180 (1994 Supp.).

  4.    The Access Board’s Subsequent Guidelines

   In 1992, the Access Board repeated its intent “to address
the issue of lines of sight over standing spectators in the
guidelines for recreational facilities which will be proposed at
a future date.” 57 Fed. Reg. 60,612, 60,618 (1992). It
requested “comments on the design issues associated with
providing integrated and dispersed accessible seating loca-
tions with a clear line of sight over standing spectators in are-
nas, stadiums or other sports facilities.” 

Board
also noted that during the initial notice and comment proce-
dures “[a]n overwhelming majority of responses favored
including a provision requiring lines of sight over standing
spectators in sports arenas and other similar assembly areas.”

1999, the Access Board finally proposed
amendments to its guidelines to address the standing specta-
tors problem. 64 Fed. Reg. 62,248, 62,501-02 (1999). These
were adopted in July 2004. 69 Fed. Reg. 44,083 (2004).
Guideline 802.2 now distinguishes between “lines of sight
over seated spectators” and “lines of sight over standing spec-
tators.” 69 Fed. Reg. at 44,391-93. Guideline 802.2.2.1 reads:
“Where standing spectators are provided lines of sight over
the heads of spectators standing in the first row in front of
their seats, spectators seated in wheelchair spaces shall be
afforded lines of sight over the heads of standing spectators
in the first row in front of wheelchair spaces.” 69 Fed. Reg.
at 44,392-93. The DOJ has not adopted the Access Board’s
2004 guidelines. Instead, the DOJ’s current regulation of lines
of sight requirements remains 28 C.F.R. pt. 36, App. A,
§ 4.33.3, as interpreted by TAM § III-7.5180 (1994 Supp.).1
  1
   The DOJ has informed us that on June 17, 2008, the DOJ published
proposed regulations that would amend the DOJ’s ADA regulations. 73
Fed. Reg. 34,508 (2008). The proposed regulations would adopt the
                   MILLER v. CALIFORNIA SPEEDWAY                     10197
B.   The Proceedings

   On October 25, 2001, Miller filed his district court com-
plaint, alleging, among other things, that Speedway violated
Title III of the ADA, 42 U.S.C. § 12181 et seq. On cross
motions for summary judgment, the district court granted
judgment for Speedway. The court acknowledged that “the
DOJ’s current position on ADAAG § 4.33.3 is reasonable”
and was consistent with Title III of the ADA and that “[w]ere
the [c]ourt to write on a clean slate, the [c]ourt would be
tempted to hold that § 4.33.3 requires lines of sight over
standing spectators.” 

, 1204.
It found, however, that the DOJ had bound itself to the Access
Board’s commentary implying that the Access Board’s 1991
guidelines (and, consequently, the DOJ’s 1991 standards) did
not address the question of lines of sight over standing specta-
tors. 

Accordingly, the court concluded that the
DOJ’s current position—found in the 1994 Supplement to the
TAM—that facilities must provide lines of sight over standing
spectators was “ ‘a fundamental modification of its previous
interpretation’ ” and had to be adopted through notice-and-
comment 

(quoting Para-
lyzed Veterans of America, 

, 586 (D.C. Cir.
1997)). It thus rejected the D.C. Circuit’s interpretation in
Paralyzed Veterans and agreed with the Third Circuit’s opin-
ion in Caruso v. Blockbuster-Sony Music Entertainment Cen-
tre, 

(3d Cir. 1999). 

. Miller appeals.2

Access Board’s 2004 guidelines, including Guideline 802.2.2.1, which
requires lines of sight over standing spectators. The regulations have not
yet been adopted, and, even if adopted, will not apply retroactively. We
understand that these are clarifying regulations, not an admission that the
DOJ’s original guidelines did not require lines of sight over standing spec-
tators.
   2
     A district court’s grant of summary judgment is reviewed de novo.
Clicks Billiards, Inc. v. Sixshooters, Inc., 

, 1257 (9th Cir.
2001). There are no genuine issues of material fact, so our sole inquiry is
whether the district court correctly applied the law. 

v. CALIFORNIA SPEEDWAY
                       II.   ANALYSIS

    We begin our analysis by stating what is not at issue in this
case. This case does not involve whether the DOJ has reason-
ably interpreted the ADA within the meaning of Chevron
U.S.A., Inc. v. NRDC, 

(1984). No party to the
litigation challenges the substantive validity of § 4.33.3, and
sensibly, no party has argued that the DOJ has exceeded its
authority under the ADA. Nor is § 4.33.3 subject to serious
challenge as “arbitrary and capricious.” See Motor Vehicle
Mfrs. Ass’n of U.S., Inc. v. State Farm Mut. Auto. Ins. Co.,

, 42-44 (1983). Although this is a private suit by
Miller against the Speedway for violating the ADA, the par-
ties all concede that the Attorney General’s lines-of-sight reg-
ulations would clearly pass muster if challenged under the
ADA. See Indep. Living 

(“DOJ rea-
sonably could have concluded that lines of sight over standing
spectators are necessary . . . . The ADA provides ample legal
authority to support such a requirement.”); see also Paralyzed

(“[A]ppellants do not contend
that the Department’s interpretation of the regulation is
unfaithful to the governing statute.”).

A.   The TAM as the DOJ’s Interpretation of Its Own
     Regulation

   [3] What is challenged here is whether the lines-of-sight
provision in the Attorney General’s 1994 Supplement to the
TAM is a valid construction of § 4.33.3. While Chevron
addresses what kind of deference we must afford an agency
in the interpretation of the statute it has been charged with
enforcing, 

, here we are dealing with the
leeway we must grant an agency in the interpretation of its
own regulations. We must give an agency’s interpretation of
its own regulations “controlling weight unless it is plainly
erroneous or inconsistent with the regulation.” Bowles v. Sem-
inole Rock & Sand Co., 

, 414 (1945). “In other
words, we must defer to the [agency’s] interpretation unless
                MILLER v. CALIFORNIA SPEEDWAY             10199
an ‘alternative reading is compelled by the regulation’s plain
language or by other indications of the [agency’s] intent at the
time of the regulation’s promulgation.’ ” Thomas Jefferson
Univ. v. Shalala, 

, 512 (1994) (quoting Garde-
bring v. Jenkins, 

, 430 (1988)). We have
explained that “[w]hen the meaning of regulatory language is
ambiguous, the agency’s interpretation controls ‘so long as it
is “reasonable,” that is, so long as the interpretation sensibly
conforms to the purpose and wording of the regulations.’ ”
Or. Paralyzed Veterans of Am. v. Regal Cinemas, Inc., 

, 1131 (9th Cir. 2003) (quoting Martin v. Occupa-
tional Safety & Health Review Comm’n, 

, 150-51
(1991)).

    Furthermore, we have previously held that the TAM itself
is entitled to substantial deference. “The guidance provided in
the technical assistance manual is an interpretation of the
DOJ’s regulation and, as such, is entitled to significant weight
as to the meaning of the regulation.” Disabled Rights Action
Comm. v. Las Vegas Events, Inc., 

, 875-76 (9th
Cir. 2004) (citations omitted). Where “[t]he DOJ’s interpreta-
tion [in the TAM] is entirely consistent with the regulation,
. . . it is due deference.” Botosan v. Paul McNally Realty, 

, 834 (9th Cir. 2000). Accordingly, “[t]he Justice
Department’s interpretation of its own regulations, such as the
Technical Assistance Manual, must also be given substantial
deference and will be disregarded only if ‘plainly erroneous
or inconsistent with the regulation.’ ” Bay Area Addiction
Research v. City of Antioch, 

, 732 n.11 (9th Cir.
1999) (quoting Thomas Jefferson 

)).

   [4] The language of § 4.33.3 requiring “lines of sight com-
parable to those for members of the general public” is ambig-
uous. Indeed, both the Third and the D.C. Circuits, although
they ultimately reach opposite conclusions on the merits,
agree that the plain language of the regulation is ambiguous
and subject to differing interpretations. See 

(“In the end it seems that both interpretations of the
10200           MILLER v. CALIFORNIA SPEEDWAY
‘lines of sight’ language are plausible.”); Paralyzed 

(“the phrase is ambiguous”). We agree that
the phrase “lines of sight” in § 4.33.3 is subject to several
interpretations.

   One possible interpretation is that the phrase means that
wheelchair patrons must have a view without physical
obstructions. See Lara v. Cinemark USA, Inc., 

,
788-89 (5th Cir. 2000). We have already held that this reading
is too narrow to be compelled by the language of § 4.33.3,
and the Attorney General is entitled to read the provision
more broadly. Regal 

.

   A more plausible interpretation of the phrase is that it
means that wheelchair areas are to be dispersed throughout a
facility, such that wheelchair users have a variety of horizon-
tal viewing angles from which to choose. See 

. This ensures that wheelchair patrons at a football
game are not all stuck, for example, behind the goalposts.
This interpretation is supported by the fact that § 4.33.3 also
requires a “choice of admission prices” to account for the dif-
ference between an end zone and a mid-field seat.

   Alternatively, the phrase can be read to require more than
horizontal dispersal; it could be read to require vertical dis-
persal as well, so that patrons have a choice of seats—for
example, between the orchestra and the loges—to obtain a
different viewing angle. Under this reading, the phrase “lines
of sight” would refer to the angle of sight between the viewer
and the stage, screen, or playing field. The latter definition of
“lines of sight” would encompass both the notion of a hori-
zontal line of sight and a vertical line of sight.

   Finally, yet another interpretation does not merely involve
the horizontal or vertical dispersal of the wheelchair seating
options, but rather suggests that the line of sight of a wheel-
chair patron must be comparable to the line of sight of a non-
wheelchair patron who has chosen the same seat. Under this
                MILLER v. CALIFORNIA SPEEDWAY              10201
interpretation it is easy to see that at some events (principally
sporting events), a “comparable” line of sight would encom-
pass an unobstructed line of sight when other patrons are
standing. When the crowd is generally standing, most specta-
tors can also stand and, in doing so, enable themselves to sub-
stantially see the event. Therefore, in order to be given a
comparable line of sight, wheelchair users must also be able
to see the event when the crowd is standing.

   Any of these interpretations would be a reasonable reading
of the ambiguous plain language of the regulation. In fact, the
phrase “lines of sight comparable to those for members of the
general public” could be interpreted to require a combination
of the proposed interpretations. That is, it is possible that a
comparable line of sight means that the view is unobstructed
by physical obstacles, that the seats must be horizontally and
vertically dispersed, and that wheelchair patrons must be able
to see over standing patrons.

   [5] In its 1994 supplement to the TAM, the DOJ made it
clear that at the very least the phrase “lines of sight compara-
ble to those for members of the general public” in § 4.33.3
required that “in assembly areas where spectators can be
expected to stand during the event or show being viewed, the
wheelchair locations must provide lines of sight over specta-
tors who stand.” TAM § III-7.5180 (1994 Supp.). The Attor-
ney General’s interpretation of § 4.33.3 is “neither plainly
erroneous [n]or inconsistent with the regulation.” Thomas Jef-
ferson 

. As a linguistic matter it is per-
fectly reasonable to interpret the term “lines of sight
comparable to those for members of the general public” as
requiring lines of sight that are comparable in the actual con-
ditions under which a facility operates. If spectators are
widely expected to stand during the key moments of an event,
then comparable lines of sight for wheelchair users could be
lines of sight that enable the wheelchair users to see during
those moments. If the spectators stand during the singing of
the national anthem, routinely jump to their feet during the
10202            MILLER v. CALIFORNIA SPEEDWAY
fourth quarter, or insist on standing on their chairs during the
third overtime, it does not take a fertile legal imagination to
understand that relatively immobile patrons will not have a
comparable line of sight.

   [6] Furthermore, the DOJ’s 1994 interpretation is consistent
with the statutory requirement that the facilities be “readily
accessible to” and “usable by” persons with disabilities. 42
U.S.C. § 12183(a)(1). To meaningfully use the Speedway
facilities, a wheelchair patron needs to be able to see the event
in the circumstances under which the race typically takes
place, with a standing audience. Otherwise the Speedway race
track is not “usable” as a practical matter. Because the DOJ’s
interpretation is a reasonable, practical construction in light of
the ambiguity of the regulation, it is entitled to substantial
deference.

   Our decision is consistent with our treatment of the DOJ’s
“comparable lines-of-sight” regulations in the context of the-
ater seating in Regal 

. The district
court had held that “the language about ‘lines of sight compa-
rable to those for members of the general public’ in § 4.33.3
does not require that wheelchair-accessible seating afford
patrons comparable viewing angles to those in non-accessible
seating.” 

(citing Oregon Paralyzed Veterans of
Am. v. Regal Cinemas, Inc., 

, 1297-98
(D. Or. 2001)). The district court had followed Lara v. Cine-
mark USA, Inc., 

(5th Cir. 2000), in which the
Fifth Circuit pointed out that “questions regarding ‘viewing
angle’ did not arise until well after the DOJ promulgated sec-
tion 4.33.3” and concluded that “lines of sight” referred to
nothing more than “unobstructed views.” 

   [7] We rejected the Fifth Circuit’s reasoning and reversed
the district court. We concluded that “lines of sight” “[i]n the
context of a movie theater, [ ] means a line extending from the
viewer’s eye to the points on the screen where the film is pro-
jected, taking into account the angle from the viewer’s eye to
                MILLER v. CALIFORNIA SPEEDWAY              10203
those points.” Regal 

. We framed
the question as “whether it is unreasonable for DOJ to inter-
pret ‘comparable line of sight’ to encompass factors in addi-
tion to physical obstructions, such as viewing angle. The
answer, in light of the plain meaning of the regulation both in
general and as understood in the movie theater industry, is
‘no.’ ” 

Accordingly, we held that DOJ’s interpre-
tation of § 4.33.3 was “valid and entitled to deference.” 

   [8] A sporting event presents a different set of challenges
from a movie theater, which has a fixed screen and relatively
placid patrons. By contrast, sporting events typically involve
live action, moving rapidly over playing surfaces many times
larger than a movie screen. When the audience—like the
athletes—is in motion, arena designers, owners and patrons
have a set of problems to address that are not present in a the-
ater setting. It was not unreasonable for the DOJ to interpret
“lines of sight” as the actual “line extending from the viewer’s
eye to the [playing field], taking into account the angle from
the viewer’s eye to those points.” 

B.   The TAM as the DOJ’s Own Interpretation of the Access
     Board Guidelines

   [9] As in Lara, a decision we declined to follow in Regal
Cinemas, the Speedway argues that the DOJ’s position is an
after-acquired view, one that “did not arise until well after the
DOJ promulgated section 4.33.3.” 

.
Indeed, the Speedway argues not just that the DOJ’s position
is an after-acquired view, but that the DOJ’s position on lines
of sight in the 1994 TAM supplement substantially departs
from the Access Board’s original commentary on lines of
sight. Asserting that the Access Board’s commentary must be
imputed to the DOJ, the Speedway contends that the DOJ’s
subsequent position is not entitled to substantial deference
because it was not promulgated according to notice and com-
ment rulemaking.
10204           MILLER v. CALIFORNIA SPEEDWAY
   The district court in this case agreed that “the board’s com-
mentary must be imputed to the DOJ,” although it also
observed that if it were “to write on a clean slate, [it] would
be tempted to hold that § 4.33.3 requires lines of sight over
standing 

. In Caruso,
the Third Circuit took a similar position, relying on

    the following factors: 1) the DOJ referred all com-
    ments to the Boards; 2) the DOJ relied on the Board
    to make adequate changes based on those comments;
    3) the Board specifically changed the language of
    4.33.3 in response to comments and explained that
    change in its commentary; 4) the DOJ was a ‘mem-
    ber of the board’ and ‘participated actively . . . in
    preparation of both the proposed and final versions
    of the [guidelines]’; and 5) the DOJ’s commentary
    stated that the final guidelines promulgated by the
    Board adequately addressed all comments.

(citations omitted).

   The district court’s point, supported by Caruso, is a fair
one. See Thomas Jefferson 

(we must
defer “unless an alternative reading is compelled by other
indications of the Secretary’s intent at the time of the regula-
tion’s promulgation”) (emphasis added; citation omitted).
After all, in its notice of proposed rulemaking, the DOJ stated
that it “propose[d] to adopt [the Access Board’s] guidelines as
the accessibility standard under this rule.” 56 Fed. Reg. at
7478-79. The same day as the Access Board published its
standards, the DOJ formally “adopt[ed] the ADAAG as the
accessibility standard” as its own. 56 Fed. Reg. at 35,585, and
on that day, the Access Board stated that “the issue of lines
of sight over standing spectators will be addressed [in the
future] in guidelines for recreational facilities.” 56 Fed. Reg.
at 35,440.
                  MILLER v. CALIFORNIA SPEEDWAY                   10205
   [10] We understand why a reasonable reader might con-
clude that as of July 1991, the DOJ’s new ADA regulations
did not address lines of sight over standing spectators. We do
not think, however, that such a reading is “compelled” by the
record. See Thomas Jefferson 

. When
the DOJ adopted the Access Board’s guidelines as its own
standards, it literally adopted the guidelines. 28 C.F.R.
§ 36.406(a) (“New construction and alterations subject to this
part shall comply with the standards for accessible design
published as appendix A to this part (ADAAG).”). It did not
adopt any other Access Board commentary, notices of pro-
posed rulemaking, or internal memoranda. Whatever the
Access Board thought of its own guidelines, the Department
of Justice adopted the text of the guidelines themselves, not
the Access Board’s interpretation of that text. The DOJ made
the Access Board’s guidelines its own, and, having done so,
it assumed responsibility for interpreting the standards.3 As
the Access Board has explained: “The Board’s guidelines
serve as the baseline for standards used to enforce the ADA
and the ABA. These standards, which are maintained by other
Federal agencies, such as the U.S. Department of Justice
under the ADA, will be updated according to the new guide-
lines. It is these standards, not the Board’s guidelines, which
the public must follow.” U.S. Access Board, Americans with
Disabilities Act and Architectural Barriers Act Accessibility
Guidelines n.p. (2004) (“Introduction”) (emphasis added).

  [11] There was good reason for the DOJ to adopt the text
of the Access Board’s guidelines. The ADA instructed the
Access Board to issue minimum guidelines within nine
  3
    The Access Board has explained the difference between its “guide-
lines” and the Attorney General’s “standards”: “Guidelines are issued by
the Board, standards by designated agencies such as DOJ . . . . ADA stan-
dards issued by DOJ . . . in 1991 based on the Board’s original ADA
Accessibility Guidelines (ADAAG) remain the standards to follow at this
time.” U.S. Access Board, Americans with Disabilities Act and Architec-
tural Barriers Act Accessibility Guidelines n.p. (2004) (“Answers to Com-
mon Questions About the New ADA-ABA Guidelines”).
10206           MILLER v. CALIFORNIA SPEEDWAY
months of enactment and ordered the Attorney General to
issue regulations within one year. 42 U.S.C. §§ 12186(b),
12204(a). By Washington standards, this required quick work.
The Access Board’s dutiful response to the mandate enabled
the DOJ to get its own regulations into print on time. More
importantly, the ADA mandated that the DOJ’s regulations
“be consistent with the minimum guidelines and requirements
issued by the [Access Board].” 42 U.S.C. § 12186(c). By for-
mally adopting the Access Board’s guidelines, the DOJ
ensured that its own regulations were “consistent with” the
Access Board’s guidelines. It seems like an easy call for the
Attorney General to piggyback on the Access Board’s hard
work at getting the ADA up and running. Those guidelines,
however, were only a launching point for the DOJ, which had
to take care that its own regulations complied with the Access
Board guidelines at a “minimum.” 

the ADA or
in the DOJ’s own regulations bound the Attorney General to
the Access Board so long as the DOJ’s regulations satisfied
some “minimum” level of equivalence. The Attorney General
was free to interpret the regulations in a manner that was
more strict than contemplated by the Access Board. There-
fore, the Access Board’s commentary should not be imputed
to the DOJ.

   Once we admit that the line-of-sight regulations are ambig-
uous, that the DOJ did not bind itself to the Access Board’s
interpretation of the guidelines, and that the Attorney General
was free to interpret the regulations in a manner that was
more strict than the Access Board’s guidelines, we have no
difficulty in concluding that the Attorney General could
resolve any ambiguity in the DOJ’s regulations by taking a
stricter view of § 4.33.3 than the Access Board did when it
adopted its guidelines. The DOJ did not have to wait for the
Access Board to act.

  Indeed, the DOJ demonstrated its independence at a very
early stage. The DOJ’s regulations became effective in Janu-
ary 1993, and it issued its first TAM that year, as required by
                 MILLER v. CALIFORNIA SPEEDWAY              10207
42 U.S.C. § 12206(c)(3). The first TAM did not address the
standing spectator problem. The following year, in 1994, the
DOJ published a supplement to the TAM and offered its first
formal interpretation of the line-of-sight rule in § 4.33.3: “in
assembly areas where spectators can be expected to stand dur-
ing the event or show being viewed, the wheelchair locations
must provide lines of sight over spectators who stand.” TAM
§ III 7.5180 (1994 Supp.). The guidance in the TAM itself is
plain; its relationship to § 4.33.3, obvious.

C.   The TAM as the DOJ’s Modification of Its Own
     Interpretive Rules

   Even if we were persuaded that the DOJ initially adopted
the Access Board’s interpretation that § 4.33.3 simply did not
address the problem of standing spectators, the DOJ may
change its mind. “The [Attorney General] is not estopped
from changing a view she believes to have been grounded
upon a mistaken legal interpretation . . . . [W]here the agen-
cy’s interpretation of [its regulation] is at least as plausible as
competing ones, there is little, if any reason not to defer to its
construction.” Good Samaritan Hosp. v. Shalala, 

, 417 (1993). The only question is whether, in order to
effectuate the change, the DOJ had to proceed through notice
and comment.

   [12] We think that, even if the DOJ’s interpretation consti-
tuted a change in the understanding of its original regulations,
the DOJ was not required to proceed by notice and comment
because both the Access Board’s original position (as imputed
to the DOJ) and the TAM would constitute interpretive rules.
See 5 U.S.C. § 553(b)(3)(A); Erringer v. Thompson, 

, 630 (9th Cir. 2004) (holding that an agency can modify
an interpretive rule without notice and comment). An inter-
pretive rule is one “issued by an agency to advise the public
of the agency’s construction of the statutes and rules which it
administers.” Shalala v. Guernsey Mem’l Hosp., 

,
99 (1995) (quotation marks and citation omitted).
10208           MILLER v. CALIFORNIA SPEEDWAY
“[I]nterpretive rules merely explain, but do not add to, the
substantive law that already exists in the form of a statute or
legislative rule,” whereas legislative rules “create rights,
impose obligations, or effect a change in existing law pursu-
ant to authority delegated by Congress.” Hemp Indus. Ass’n
v. DEA, 

, 1087 (9th Cir. 2003).

   [13] In one sense, the 1994 Supplement to the TAM
imposed obligations that might not have been anticipated. We
understand how, from the perspective of facility owners such
as Speedway, the 1994 Supplement appears to be a legislative
rule. On the other hand, the 1994 Supplement added nothing
to the existing rule except a definition of an ambiguous term;
it merely clarified the DOJ’s view of the scope of § 4.33.3.
That is the purpose of an interpretive rule. A rule does not
become a legislative rule because it effects some unantici-
pated change; otherwise, only superfluous rules could qualify
as interpretive rules. See 

(rejecting
the argument that notice and comment must apply “where one
unpublished policy is replaced by a revised version of that
policy that significantly affects members of the public.”) We
do not think that interpretive rules must be so useless. In sum,
we conclude that the 1994 Supplement to the TAM was an
interpretive rule and, even if it reflected a change in the DOJ’s
thinking about comparable lines of sight, it was a reasonable
interpretation of an ambiguous regulation that did not require
notice and comment prior to publication.

                              III.

  The regulatory scheme at issue in this case is complex, but
our conclusion is simple: the DOJ’s interpretation of its own
regulation is reasonable and therefore entitled to substantial
deference. The judgment is REVERSED.