FOR PUBLICATION
 UNITED STATES COURT OF APPEALS
      FOR THE NINTH CIRCUIT

UNITED STATES OF AMERICA,                No. 04-30316
                Plaintiff-Appellee,
                                            D.C. No.
               v.
                                         CR-02-00036-
JOEL ANDREW WYATT, aka                     DWM/LBE
“Lupine”; REBECCA KAY SMITH,
                                           OPINION
           Defendants-Appellants.
                                      
       Appeal from the United States District Court
         for the District of Montana (Missoula)
       Donald W. Molloy, District Judge, Presiding

                  Argued and Submitted
          February 8, 2005—Seattle, Washington

                    Filed May 26, 2005

 Before: Diarmuid F. O’Scannlain, M. Margaret McKeown,
             and Carlos T. Bea, Circuit Judges.

                   Opinion by Judge Bea




                           5801
                  UNITED STATES v. WYATT               5803


                        COUNSEL

David C. Avery, Federal Defenders of Montana, argued the
cause for the appellant. John Rhodes and Jon Wilson, Federal
Defenders of Montana, were also on the briefs.

Joshua S. Van De Wetering, Office of the U.S. Attorney,
argued the cause for the appellee. William W. Mercer, Office
of the U.S. Attorney, was also on the brief.
5804                 UNITED STATES v. WYATT
                            OPINION

BEA, Circuit Judge:

   Joel A. Wyatt and Rebecca Kay Smith (collectively “defen-
dants”) appeal their convictions for (1) using, or aiding and
abetting the use of, a hazardous or injurious device on federal
land with the intent to obstruct a timber harvest; and (2) main-
taining an unauthorized structure on National Forest land. We
have jurisdiction under 28 U.S.C. § 1291. We consider below
whether 18 U.S.C. § 1864(a), which in part prohibits the use
of hazardous or injurious devices on federal land with the
intent to obstruct or harass the harvesting of timber, is uncon-
stitutionally vague as applied here to visible and unmodified
ropes strung above a proposed helicopter landing site.1 We
conclude the statute is not unconstitutionally vague as
applied, and thus we affirm.

                             FACTS

   On July 8, 2002, defendants Wyatt and Smith, members of
Wild Rockies Earth First!, ascended and occupied separate
elevated platforms in two trees as part of a “tree-sitting” pro-
test in the Bitterroot National Forest in Montana. Smith’s plat-
form was forty-five feet up in a tree, and Wyatt’s platform
was eighty to ninety feet up in a tree. Defendants occupied the
platforms for several weeks to protest logging. The protest
site was on National Forest Service land.

   The protest site had earlier been designated as (1) a pro-
posed logging helicopter landing site, and (2) an emergency
medical helicopter landing site. At the time of the protest,
however, the site could not yet be used for logging helicop-
ters; safety standards required an expanded site, which in turn
  1
    We decide defendants’ remaining contentions by memorandum dispo-
sition filed concurrently with this opinion.
                       UNITED STATES v. WYATT                         5805
required the removal of about five trees.2 A “natural opening”
existed at the site, however, that would allow emergency
medical helicopters, or other helicopters, to land (e.g., if the
helicopters suffered engine failure).

   A blue climbing rope was strung between the defendants’
platforms, and four yellow polypropylene ropes were strung
from the trees. The yellow ropes were not suitable for climb-
ing. The ropes were tied within reach of the platforms occu-
pied by defendants. The ropes were repositioned during the
time defendants occupied their respective platforms, although
the testimony did not identify by whom.

   Donald Polanski, a U.S. Forest Service law enforcement
officer, testified the purpose of the yellow ropes was to inter-
fere with helicopters operating at the site, and thus prevented
logging activity there. Bret Daugherty, a forester with Carson
Helicopters, testified the use of the ropes interfered with log-
ging activities because the landing site could not be used.
Specifically, the yellow ropes would interfere with logging
helicopters because the 200-foot line used by the helicopters
could entangle with the yellow ropes. The yellow ropes could
also entangle with a helicopter’s rotors, air intake, or fuselage,
and thus cause a crash.

   Both defendants stated that when they volunteered to par-
ticipate in the tree sit, they knew the protest site was chosen
to prevent helicopters from landing. They knew the purpose
of the lines and wires was to interfere with helicopter opera-
tions at the site, knew that their presence in the trees by itself
would hinder helicopter landings in the protest area, and were
in a position to assert control over the yellow ropes. Further,
there was evidence the ropes were tied to the trees occupied
  2
   Logging helicopters attach a 200-foot line to logs and then deposit the
logs into the landing site. The logging helicopter does not actually land at
the site, but instead lowers the log where it is grasped by loggers working
on the ground.
5806                UNITED STATES v. WYATT
by defendants, within reach of defendants (themselves four to
nine stories above the ground), and that the ropes were
adjusted during the time defendants were stationed in their
respective trees.

   Wyatt eventually descended from his platform on July 29,
2002, but Smith remained in the tree until August 6, 2002,
when the U.S. Forest Service removed her from her platform.
The government charged defendants with four counts; only
Count 1 is relevant to this opinion. Count 1 alleged defen-
dants, “with the intent to obstruct or harass the harvesting of
timber, used, or aided and abetted the use of, a hazardous or
injurious device capable of causing bodily injury or damage
to property, to wit: lines or wires, on Federal land, in violation
of 18 U.S.C. § 1864 and 18 U.S.C. § 2.” After a consolidated
trial, the jury returned a guilty verdict on Count 1. Defendants
timely appealed.

                        DISCUSSION

   Defendants contend 18 U.S.C. § 1864(a) is unconstitution-
ally vague as applied here because the statute “does not sup-
ply adequate notice that it is a crime to hang unmodified and
highly visible ropes between trees” because “unmodified and
highly visible ropes” do not fall within the statute’s definition
of a “hazardous or injurious device.” We review de novo
whether a statute is unconstitutionally vague. United States v.
Rodriguez, 

, 953 (9th Cir. 2004).

   [1] In an as-applied challenge, a statute is void for vague-
ness (and thus unconstitutional under due process) if the stat-
ute “(1) does not define the conduct it prohibits with sufficient
definiteness and (2) does not establish minimal guidelines to
govern law enforcement.” 

see United States v.
Hockings, 

, 1072 (9th Cir. 1997) (a criminal
statute “cannot be so vague that men of common intelligence
must necessarily guess at its meaning and differ as to its
application.”) (internal quotation marks omitted). As a corol-
                        UNITED STATES v. WYATT                         5807
lary to the vagueness doctrine, where the statute is ambigu-
ous, “the rule of lenity must be applied to restrict criminal
statutes to conduct clearly covered by those statutes.” Hock-

.

   [2] In determining whether 18 U.S.C. § 1864(a) provided
fair warning to defendants that it is a crime to hang “unmodi-
fied and highly visible ropes between trees” over a proposed
helicopter landing site, we first look to the statute. 18 U.S.C.
§ 1864(a) provides:

     Whoever— (1) with the intent to violate the Con-
     trolled Substances Act, (2) with the intent to obstruct
     or harass the harvesting of timber, or (3) with reck-
     less disregard to the risk that another person will be
     placed in danger of death or bodily injury and under
     circumstances manifesting extreme indifference to
     such risk, uses a hazardous or injurious device on
     Federal land, . . . without the consent of the United
     States shall be punished under subsection (b).

   [3] Only subsection (2) is at issue here. The statute defines
“hazardous or injurious device” generally as “a device, which
when assembled or placed, is capable of causing bodily
injury, or damage to property, by the action of any person
making contact with such device subsequent to the assembly
or placement.” 18 U.S.C. § 1864(d)(3). The definition of
“hazardous or injurious device” also includes “sharpened
stakes, lines or wires, lines or wires with hooks attached,” and
others. 18 U.S.C. § 1864(d)(3) (emphasis added).3
   3
     The full definition of “hazardous or injurious device” reads: “a device,
which when assembled or placed, is capable of causing bodily injury, or
damage to property, by the action of any person making contact with such
device subsequent to the assembly or placement. Such term includes guns
attached to trip wires or other triggering mechanisms, ammunition
attached to trip wires or other triggering mechanisms, or explosive devices
attached to trip wires or other triggering mechanisms, sharpened stakes,
5808                   UNITED STATES v. WYATT
   [4] For several reasons, section 1864(a) provides fair warn-
ing to persons of common intelligence that it is a crime to
hang ropes above a helicopter landing site with the intent to
obstruct or harass the harvesting of timber. See Hock

. First, unmodified and visible ropes strung above
a helicopter landing site meet the general definition of a “haz-
ardous or injurious device”: when “assembled or placed,”
(i.e., strung above the landing site), the ropes are “capable of
causing bodily injury, or damage to property, by the action of
any person making contact with such device subsequent to the
assembly or placement” (i.e., if the helicopter should land
upon or become entangled in the ropes, it is likely to crash).

   [5] Second, the definition of a “hazardous or injurious
device” includes “sharpened stakes, lines or wires, lines or
wires with hooks attached,” and others. 18 U.S.C.
§ 1864(d)(3). The term “lines” is generally defined as “[a]
rope, cord, [or] string.” Oxford English Dictionary (2d ed.
1989). Thus, the yellow ropes fall with the “lines or wires”
example.

   [6] Third, the examples listed in the “hazardous and injuri-
ous device” definition readily show Congress’ intent was to
prevent interference with logging activities by the use of
devices that might cause “bodily injury” or “damage to prop-
erty.” For example, the definition of “hazardous or injurious
device” includes inter alia “tree spiking devices.” 18 U.S.C.
§ 1864(d)(3). Legislative history also supports this conclu-
sion. Senator McClure stated 18 U.S.C. § 1864 was intended
to stop ecoterrorists from using “dangerous and deadly” meth-
ods to further their goals. 134 Cong. Rec. S16,064-65 (daily

lines or wires, lines or wires with hooks attached, nails placed so that the
sharpened ends are positioned in an upright manner, or tree spiking
devices including spikes, nails, or other objects hammered, driven, fas-
tened, or otherwise placed into or on any timber, whether or not severed
from the stump.” 18 U.S.C. § 1864(d)(3).
                   UNITED STATES v. WYATT                  5809
ed. Oct. 14, 1988). He detailed some of the hazardous “tools
of the ecoterrorist’s trade,” including punji sticks—steel bars
with sharpened nails that can injure unsuspecting hikers—and
tree spikes—spikes driven into trees that shatter saw blades
into dangerous shrapnel. 

clear Congress intended this
statute to prevent the use of those and other devices that are
hazardous and injurious to logging activities.

   [7] In determining whether a statute is void for vagueness,
we also consider whether the statute defines the offense “in
such a manner that does not encourage arbitrary and discrimi-
natory enforcement.” Kolendar v. Lawson, 

, 357
(1983). A scienter requirement can help a law escape a vague-
ness problem. Posters ‘N Things, Ltd. v. United States, 

, 526 (1994). Section 1864 contains just such a
scienter requirement: it does not simply prohibit the use of a
“hazardous or injurious device,” but requires a defendant to
use the device “with the intent to obstruct or harass the har-
vesting of timber.” See 18 U.S.C. § 1864(a)(2). The intent
requirement thus limits the discretion of law enforcement and
mitigates any perceived vagueness of 18 U.S.C. § 1864.

   Defendants misconstrue section 1864(a) by arguing the
statute does not provide sufficient notice because “unmodified
and highly visible ropes” are not included within the defini-
tion of a “hazardous and injurious device” in section
1864(d)(3). The exclusion of unmodified and visible ropes
from this non-exhaustive list does not remove the ropes from
the ambit of the definition of “hazardous and injurious
device.” As noted, the definition begins with a general defini-
tion (which, in any event, would encompass the yellow ropes)
and then provides a list of devices “include[d]” under the defi-
nition. The use of the word “includes” suggests the list is non-
exhaustive rather than exclusive. See 

; see also Federal Land Bank v. Bismarck Lumber Co.,

, 100 (1941) (“the term ‘including’ is not one of
all-embracing definition, but connotes simply an illustrative
application of the general principle.”).
5810               UNITED STATES v. WYATT
   Defendants also argue that in the “hazardous or injurious
device” definition, the word “sharpened” modifies “stakes”
and “lines or wires.” Thus, because the ropes here were not
“sharpened,” they do not fall within the definition. We dis-
agree. The error of defendants’ argument becomes clear when
the phrase “sharpened stakes, lines or wires, lines or wires
with hooks attached” from 18 U.S.C. § 1864(d)(3) is com-
pared with 21 U.S.C. § 841(d)(1). There, Congress provided
that “[a]ny person who assembles, maintains, places, or
causes to be placed a boobytrap on Federal property where a
controlled substance is being manufactured, distributed, or
dispensed shall be sentenced to a term of imprisonment . . . .”
21 U.S.C. § 841(d)(1). That statute defines “boobytrap” as
“any concealed or camouflaged device designed to cause bod-
ily injury when triggered by any action of any unsuspecting
person making contact with the device. Such term includes
guns, ammunition, or explosive devices attached to trip wires
or other triggering mechanisms, sharpened stakes, and lines
or wires with hooks attached.” 21 U.S.C. § 841(d)(3) (empha-
sis added). Notably, the unmodified term “lines or wires” is
missing from that statute, which suggests Congress did not
intend in 18 U.S.C. § 1864(d)(3) to modify the term “lines
and wires” with the word “sharpened.”

   [8] Accordingly, we hold that 18 U.S.C. § 1864(a) provides
fair warning to a person of common intelligence that it is a
crime to hang ropes over a helicopter landing site with the
intent to obstruct or harass the harvesting of timber. The stat-
ute is thus not unconstitutionally void for vagueness as
applied here.

   [9] For the same reasons, the rule of lenity is inapplicable
here. “Under the rule of lenity, when a criminal statute is
ambiguous, we interpret the statute in favor of the defendant.
However, it applies only when there is grievous ambiguity or
uncertainty in the statute and when, after seizing everything
from which aid can be derived, we can make no more than a
guess as to what Congress intended.” United States v. Phil-
                   UNITED STATES v. WYATT                  5811
lips, 

, 857 n.39 (9th Cir. 2004) (internal alter-
ations, citations, and quotation marks omitted). Although 18
U.S.C. § 1864(d)(3) generally focuses upon concealed hazard-
ous or injurious devices, such as tree spikes or trip wires, the
statute is not ambiguous as applied because it is clear how the
yellow ropes could be hazardous or injurious to a helicopter
should a helicopter come into contact with the ropes.

  AFFIRMED.