 United States Court of Appeals
         FOR THE DISTRICT OF COLUMBIA CIRCUIT



Argued March 18, 2016                 Decided July 29, 2016

                        No. 14-5326

 CONFEDERATED TRIBES OF THE GRAND RONDE COMMUNITY
                    OF OREGON,
                     APPELLANT

                            v.

SALLY JEWELL, IN HER OFFICIAL CAPACITY AS SECRETARY OF
THE UNITED STATES DEPARTMENT OF THE INTERIOR, ET AL.,
                      APPELLEES


                Consolidated with 15-5033


       Appeals from the United States District Court
               for the District of Columbia
                   (No. 1:13-cv-00849)


    Lawrence Robbins argued the cause for appellants
Confederated Tribes of the Grand Ronde Community of
Oregon. With him on the briefs were Gary A. Orseck, and
Daniel N. Lerman.

    Benjamin S. Sharp argued the cause for appellants Clark
County, Washington, et al. With him on the briefs were
Jennifer A. MacLean, Donald C. Baur, Eric D. Miller, Brent
D. Boger, and Christine M. Cook.
                               2

    John L. Smeltzer, Attorney, U.S. Department of Justice,
argued the cause for federal appellees. With him on the brief
were John C. Cruden, Assistant Attorney General, and
Elizabeth Ann Peterson, Attorney.

     Robert D. Luskin argued the cause for intervenor-
appellee the Cowlitz Indian Tribe. With him on the brief
were V. Heather Sibbison, Suzanne R. Schaeffer, and Kenneth
J. Pfaehler.

     Craig J. Dorsay was on the brief for amicus curiae
Samish Indian Nation in support of federal appellee Sally
Jewell, Secretary of the United States Department of the
Interior, and intervenor-appellee Cowlitz Indian Tribe.

    Elliott A. Milhollin, Gregory A. Smith, and Geoffrey D.
Strommer were on the brief for amici curiae United South and
Eastern Tribes, Inc. and Jamestown S’Klallam Tribe in
support of intervenor-appellee.

   Before: PILLARD and WILKINS, Circuit Judges, and
EDWARDS, Senior Circuit Judge.

     WILKINS, Circuit Judge: The Cowlitz are an American
Indian tribe from southwestern Washington state. After
refusing to sign a land cession treaty with the United States in
1855, President Lincoln by 1863 proclamation opened its land
to non-Indian settlement. Without a land base, the Cowlitz
scattered, and for decades federal Indian policy reflected a
mistaken belief that they no longer existed as a distinct
communal entity.       After a formal process for federal
acknowledgment came into being in 1978, the Cowlitz at last
gained legal status as a tribe in the eyes of the government in
2002.      Reconsidered Final Determination for Federal
                                3
Acknowledgment of the Cowlitz Indian Tribe, 67 Fed. Reg.
607 (Jan. 4, 2002). Immediately thereafter, they successfully
petitioned the Department of the Interior to take into trust and
declare as their “initial reservation” a parcel of land. The
Cowlitz wish to use this parcel for tribal government
facilities, elder housing, a cultural center, as well as a casino.

     Two groups of Plaintiff-Appellants bring challenges
under the Administrative Procedure Act (“APA”), 5 U.S.C.
§ 551 et seq., to the Interior Secretary’s decision to take the
land into trust and to allow casino-style gaming. One group 1
is comprised of Clark County, Washington, homeowners and
community members in the area surrounding the parcel, as
well as competing gambling clubs and card rooms
(collectively, “Clark County”). Another is the Confederated
Tribes of the Grand Ronde Community of Oregon (“Grand
Ronde”), which owns and operates a competing casino. The
District Court consolidated the actions, allowed the Cowlitz to
intervene and, in reviewing cross-motions for summary
judgment, ruled in favor of the Secretary and the Cowlitz.
See Confederated Tribes of the Grand Ronde Cmty. v. Jewell,
75 F. Supp. 3d 387 (D.D.C. 2014).

    For the reasons that follow, we affirm the judgment of the
District Court. The Secretary reasonably interpreted and
applied the Indian Reorganization Act (“IRA”), 25 U.S.C.
§ 461 et seq., to conclude that the Cowlitz are a “recognized
Indian tribe now under Federal jurisdiction,” 25 U.S.C. § 479.
The Secretary also reasonably determined that the Cowlitz
meet the “initial-reservation” exception to the Indian Gaming
Regulatory Act (“IGRA”), 25 U.S.C. § 2701 et seq. Lastly,

1
  The City of Vancouver, Washington, was voluntarily dismissed
from the case following oral argument.
                               4
we reject Appellants’ remaining claims of error under the
IRA, the National Environmental Policy Act (“NEPA”), 42
U.S.C. § 4321 et seq., and 25 C.F.R. § 83.12(b) (1994), based
on the Secretary’s alleged failure independently to verify the
Tribe’s business plan and membership figures.

                               I.

     The 1934 IRA was meant “to promote economic
development among American Indians, with a special
emphasis on preventing and recouping losses of land caused
by previous federal policies.” Mich. Gambling Opposition v.
Kempthorne, 525 F.3d 23, 31 (D.C. Cir. 2008). Whereas a
prior policy of allotment sought “to extinguish tribal
sovereignty, erase reservation boundaries, and force the
assimilation of Indians into the society at large,” Cty. of
Yakima v. Confederated Tribes & Bands of Yakima Indian
Nation, 502 U.S. 251, 254 (1992), Congress enacted the IRA,
among other things, to “conserve and develop Indian lands
and resources,” Pub. L. No. 383, 48 Stat. 984, 984 (1934).
As part of this effort, the statute permits the Secretary of the
Interior to accept lands into federal trust for “Indians.”
25 U.S.C. § 465.

   There are three ways to qualify as an “Indian” under the
IRA, which extends to:

       [1] [A]ll persons of Indian descent who are
       members of any recognized Indian tribe now
       under Federal jurisdiction . . .

       [2] [A]ll persons who are descendants of
       such members who were, on June 1, 1934,
       residing within the present boundaries of any
       Indian reservation, and . . .
                                5

       [3] [A]ll other persons of one-half or more
       Indian blood.

25 U.S.C. § 479. In Carcieri v. Salazar, the Supreme Court
held that the word, “now,” unambiguously limits the first
definition to members of those tribes that were under federal
jurisdiction in the year 1934. 555 U.S. 379, 391 (2009). In
so holding, it did not pass on the exact meaning of
“recognized” or “under Federal jurisdiction.” These two
terms are at the heart of our case.

     Appellants challenge whether the Cowlitz qualify as
“Indians” under the IRA because another statute – the
IGRA – permits gaming on land that the Secretary takes into
trust on behalf of Indians pursuant to the IRA. 25 U.S.C.
§ 2719. For lands acquired after October 17, 1988, there is a
blanket prohibition on IGRA-regulated gaming, id. § 2719(a),
unless the land meets certain statutory criteria, id. § 2719(b).
Pertinent to our case, the IGRA contains an exception for
land acquired as part of “the initial reservation of an Indian
tribe acknowledged by the Secretary under the Federal
acknowledgment process” – the so-called “initial-reservation”
exception. Id. § 2719(b)(1)(B)(ii). Another exception – for
so-called “restored lands” – applies where land has been
acquired as part of “the restoration of lands for an Indian tribe
that is restored to Federal recognition.”                      Id.
§ 2719(b)(1)(B)(iii). These exceptions “ensur[e] that tribes
lacking reservations when [the] IGRA was enacted are not
disadvantaged relative to more established ones.” City of
Roseville v. Norton, 348 F.3d 1020, 1030 (D.C. Cir. 2003).
For the whole point of the IGRA is to “provide a statutory
basis for the operation of gaming by Indian tribes as a means
of promoting tribal economic development, self-sufficiency,
and strong tribal governments.” Diamond Game Enters. v.
                                6
Reno, 230 F.3d 365, 366-67 (D.C. Cir. 2000) (quoting 25
U.S.C. § 2702(1)).

     After an Indian Claims Commission (“ICC”) 2 decision
concluded that the federal government had “deprived the
Cowlitz Tribe of its aboriginal title as of March 20, 1863,
without the payment of any consideration therefor,” 3 25 Ind.
Cl. Comm. 442, 463 (June 23, 1971), it was not until years
later in 2002 that the Tribe gained federal acknowledgment. 4
Final Determination to Acknowledge the Cowlitz Indian
Tribe, 65 Fed. Reg. 8,436 (Feb. 18, 2000); 67 Fed. Reg. at
607. The federal acknowledgment process requires an
applicant group to show, inter alia, that it has existed as a
distinct community since 1900. See 25 C.F.R. § 83.11(b).
The acknowledgment conferred on the Cowlitz legal status as
an Indian tribe, thereby qualifying them for the protection,
services, and benefits afforded by the federal government to
Indian tribes. FELIX S. COHEN’S HANDBOOK OF FEDERAL
INDIAN LAW 134 (2012 ed.) [hereinafter Cohen].

    The same day the Cowlitz gained federal
acknowledgment, they submitted an application to Interior
2
 The ICC no longer exists but was a special tribunal created to try
pre-1946 Indian claims against the federal government. Six Nations
Confederacy v. Andrus, 610 F.2d 996, 997 (D.C. Cir. 1979).
3
 In 1973, the ICC entered judgment in favor of the Cowlitz for
$1,550,000. 30 Ind. Cl. Comm. 129, 143 (April 12, 1973).
4
  Following an administrative appeal and remand, in December
2001, the Assistant Secretary for Indian Affairs issued a
Reconsidered Final Determination affirming the earlier one. J.A.
1143. The Reconsideration was published in the Federal Register
on, and federal acknowledgment was effective as of, January 4,
2002. 67 Fed. Reg. 607 (Jan. 4, 2002).
                                 7
requesting that it accept into trust and declare a 151.87-acre
parcel of land their “initial reservation.” The parcel is located
in Clark County, Washington, closest to the town of La
Center, and is approximately 24 miles from the Tribe’s
headquarters in Longview, Washington, 30 minutes from
Portland, Oregon, and 20 minutes from Vancouver,
Washington. Grand Ronde’s casino, in comparison, is located
approximately 65 miles from Portland. The parties dispute
the Cowlitz’s historical connections to the parcel, but at least
agree that it is 14 miles south of Cowlitz aboriginal territory,
where the tribe exercised exclusive use and occupancy.

     As part of the tribal gaming approval process, while the
initial-reservation request and land-into-trust petition were
pending with Interior, the National Indian Gaming
Commission (“NIGC”) 5 issued a 2005 Opinion suggesting
that the parcel also could qualify for the IGRA’s restored-
lands exception. 6 The Bureau of Indian Affairs next prepared
a draft environmental impact statement (“DEIS”) and final
environmental impact statement (“FEIS”) in 2006 and 2008,
respectively. See 42 U.S.C. § 4332(C) (requiring a detailed
environmental impact statement for “major Federal actions
significantly affecting the quality of the human
environment”). In 2010, the Secretary initially approved the

5
   Congress created the NIGC, an independent regulatory
commission located within the Interior Department, to implement
the IGRA. See Diamond Game Enters., 230 F.3d at 367; Cohen at
876 n.5.
6
  The tribe noted that it was effectively asking to qualify for both
exceptions – one through the Secretary and one through the NIGC.
At the time there was no prohibition on qualifying for both
exceptions at the same time, but that changed in 2008. See
Confederated Tribes, 75 F. Supp. 3d at 395 n.3 (citing 25 C.F.R.
§ 292.6 (2008)); 25 C.F.R. § 292.11(b)(2) (2008).
                               8
land-trust application, and declared the land to be the initial
reservation of the Cowlitz. Following a separate APA
challenge and remand, Interior issued a revised record of
decision (“ROD”) in April 2013 that, among other things,
confirmed its initial reservation decision.

     Grand Ronde and Clark County each challenged the final
ROD in June 2013. They alleged: 1) that the Cowlitz were
neither “recognized” nor “under federal jurisdiction” in 1934,
and therefore cannot be the beneficiary of a trust acquisition
under the IRA; 2) that the Tribe lacks sufficient historic
connections to the parcel to meet the regulatory requirements
for the IGRA’s initial-reservation exception; and 3) that the
FEIS failed, in various ways, to satisfy the requirements of the
National Environmental Policy Act.               Clark County
additionally claimed that the Secretary lacked authority to
take the land into trust because it allegedly shirked a
responsibility under 25 C.F.R. § 83.12(b) (1994) regarding
additions to a tribe’s membership roll after federal
acknowledgment.

     The District Court consolidated the actions, allowed the
Cowlitz to intervene as a defendant, and granted summary
judgment for Interior and the Cowlitz. This appeal timely
followed.

                              II.

    We review the District Court’s grant of summary
judgment de novo. TOMAC, Taxpayers of Michigan Against
Casinos v. Norton, 433 F.3d 852, 860 (D.C. Cir. 2006). We
will not uphold an agency decision that is “arbitrary,
capricious, an abuse of discretion, or otherwise not in
accordance with law,” 5 U.S.C. § 706(2)(A), or “unsupported
by substantial evidence,” 5 U.S.C. § 706(2)(E).
                                9

     When it comes to an agency’s interpretation of a statute
Congress has authorized it to implement, we employ the
familiar Chevron analysis. Citizens Exposing Truth About
Casinos v. Kempthorne, 492 F.3d 460, 465 (D.C. Cir. 2007)
(citing Chevron v. Natural Res. Def. Council, Inc., 467 U.S.
837 (1984)). If Congress has directly spoken to the issue, that
is the end of the matter. Id. (citing Chevron, 467 U.S. at 842-
43). Otherwise, in cases of implicit legislative delegation, we
must determine if the agency’s interpretation is permissible,
and if so, defer to it. Id; Chevron, 467 U.S. at 843-44. We do
so while mindful of the “governing canon of construction
requir[ing] that statutes are to be construed liberally in favor
of the Indians, with ambiguous provisions interpreted to their
benefit.” California Valley Miwok Tribe v. United States, 515
F.3d 1262, 1266 n.7 (D.C. Cir. 2008) (quoting Cobell v.
Norton, 240 F.3d 1081, 1101 (D. C. Cir. 2001)). Of course,
agency action is always subject to arbitrary and capricious
review under the APA, even when it survives Chevron Step
Two – an inquiry that in our case overlaps. See Judulang v.
Holder, 132 S. Ct. 476, 483 n.7 (2011); see also EDWARDS ET
AL., FEDERAL STANDARDS OF REVIEW 217-220 (2d ed. 2013).
Finally, we give substantial deference to an agency’s
interpretation of its own regulations unless it is contrary to the
regulation’s plain language. Thomas Jefferson Univ. v.
Shalala, 512 U.S. 504, 512 (1994).

                               A.

    The Secretary’s authority to take land into trust is limited,
in pertinent part, to doing so on behalf of “any recognized
Indian tribe now under Federal jurisdiction.” 25 U.S.C.
§ 479. Appellants challenge the Secretary’s decision with
respect to both what it means to be “recognized” and to be
                              10
“under Federal jurisdiction.” We first tackle the meaning of
“recognized.”

                              1.

     The Secretary determined that the Cowlitz’s federal
acknowledgment in 2002 satisfied the statute’s recognition
requirement.     The Secretary began by explaining that,
although “now under Federal jurisdiction” refers to when the
IRA was enacted, “now” is cabined to that Federal-
jurisdiction requirement and does not modify “recognized.”
Citing Justice Breyer’s approach from his concurrence in
Carcieri, the ROD explained that “[t]he IRA imposes no time
limit upon recognition,” J.A. 255 (quoting 555 U.S. at 398
(Breyer, J., concurring)), and “the tribe need only be
‘recognized’ as of the time the Department acquires the land
into trust,” J.A. 255. Thus, there was no need to further
delineate the precise contours of the term, which the Secretary
acknowledged carries much historical baggage. The concept
of “recognition” has been used at once in the cognitive or
quasi-anthropological sense, in terms of knowing or realizing
that a tribe exists, and alternatively in a political sense, to
refer to a formalized, unique relationship between a tribe and
the United States. Rather than parse the range of interactions
with the government qualifying as recognition, the Secretary
concluded that under any definition, the Cowlitz’s 2002
acknowledgment through the administrative federal
acknowledgment process was sufficient. J.A. 254-55.

     According to Appellants, the Secretary’s interpretation
was error because the IRA mandates that a tribe must have
been recognized in the year 1934. When it comes to the
meaning of recognition, they furthermore believe the IRA
uses that term in the political sense. Appellants advocate that
there must have been some “formal political act confirming
                               11
the tribe’s existence as a distinct political society” back in in
1934, which, they maintain, the Cowlitz cannot show. Grand
Ronde Br. 19 (citing California Valley Miwok, 515 F.3d at
1263).

                               2.

     We first confront whether Congress has directly spoken
to the issue, an inquiry we undertake using traditional tools of
statutory interpretation, and decide it has not. Chevron, 467
U.S. at 842 n.9; Consumer Elecs. Ass’n v. FCC, 347 F.3d 291,
297 (D.C. Cir. 2003).

      Before moving to Chevron Step One, though, we pause to
confirm that the Chevron framework is in fact applicable.
Clark County suggests that the Supreme Court already
foreclosed any role by Interior to interpret the first definition
of Indian in the IRA. Clark County Br. 9-10 (citing Carcieri,
555 U.S. at 391). That is too broad a reading of Carcieri,
whose holding reaches only the temporal limits of the
Federal-jurisdiction prong. 555 U.S. at 395. (“We hold that
the term ‘now under Federal jurisdiction’ in § 479
unambiguously refers to those tribes that were under the
federal jurisdiction of the United States when the IRA was
enacted in 1934.”). When the Court in another passage wrote
that there was “no gap in 25 U.S.C. § 479 for the agency to
fill,” Carcieri, 555 U.S. at 391, it was rejecting a government
argument that the IRA’s three definitions of “Indian” were
“illustrative rather than exclusive,” Brief for Respondents at
26, Carcieri v. Salazar, 555 U.S. 379 (2009) (No. 07-526).
The Court disagreed that the statute’s phrasing somehow
empowered Interior to create additional categories of Indians.
See Carcieri, 555 U.S. at 391 (citing Brief for Respondents at
26-27). That sentence does not mean, however, that the IRA
is wholly immune to a Chevron analysis.
                             12
    We thus turn to the text of the statute, which defines
“Indian” as:

       [1] [A]ll persons of Indian descent who are
       members of any recognized Indian tribe now
       under Federal jurisdiction . . .

       [2] [A]ll persons who are descendants of
       such members who were, on June 1, 1934,
       residing within the present boundaries of any
       Indian reservation, and . . .

       [3] [A]ll other persons of one-half or more
       Indian blood.

25 U.S.C. § 479. When considering the larger phrase,
“recognized Indian Tribe now under Federal jurisdiction,” the
word, “now” is an adverb, and adverbs modify verbs,
adjectives or other adverbs. MICHAEL STRUMPF & AURIEL
DOGULAS, THE GRAMMAR BIBLE 112 (2004). Adverbs
typically precede the adjectives and adverbs they seek to
modify, which strongly signals that “now” is limited to the
prepositional phrase, “now under Federal jurisdiction.” See
id. at 121. The placement of “now” in reference to “under
Federal jurisdiction” is only half the answer, however. The
more difficult question is whether that temporally limited
prepositional phrase, “now under Federal jurisdiction,”
modifies the noun, “tribe,” before its modification by the
adjective, “recognized,” or whether it modifies the already
modified noun, “recognized tribe.” If “now under Federal
jurisdiction” only modifies “tribe,” there is no temporal
limitation on when recognition must occur.            If the
prepositional phrase instead modifies “recognized tribe,”
recognition must have already happened as of 1934. See
Carcieri, 555 U.S. at 391.
                              13
     Understood in this way, we agree with the District Court
that “recognized” is ambiguous and susceptible to either
interpretation. While Appellants disagree, Grand Ronde
offers a grammatical hypothetical that only confirms this
ambiguity. When considering a statute giving benefits to
“any certified veteran wounded in 1934,” Grand Ronde Br.
12, that phrase might very well refer to a universe of veterans
wounded in 1934, but thereafter certified, Confederated
Tribes, 75 F. Supp. 3d at 399.          Like in our situation,
“wounded in 1934” modifies the noun, “veteran.” But
“veteran” is also modified by “certified,” and it is unclear
from the sentence’s structure when the certification must
occur. Grande Ronde’s own example shows that Appellants’
construction “is not an inevitable one.” Regions Hosp. v.
Shalala, 522 U.S. 448, 460 (1998); see also id. at 458 (“[T]he
phrase ‘recognized as reasonable’ might mean costs the
Secretary . . . has recognized as reasonable . . . or will
recognize as reasonable”).

      The structure of the IRA does not counsel otherwise.
Appellants contend that the IRA’s second definition of
“Indian” erases any ambiguity in the first definition and does
not make sense unless we understand the statute to require
recognition in 1934. The second definition refers to “all
persons who are descendants of such members who were, on
June 1, 1934, residing within the present boundaries of any
Indian reservation.” 25 U.S.C. § 479. Appellants do not
believe a descendant of a tribe recognized in 2002 could have
lived on a reservation in 1934. That assumption is incorrect,
for, as the government explains, recognition that occurs after
1934 “simply means, in retrospect, that any descendant of a
Cowlitz Tribal member who was living on an Indian
reservation in 1934 then met the IRA’s second definition.”
Gov’t Br. 47. As a concrete example, the District Court
pointed to Cowlitz members who lived on the reservation of
                              14
the Quinault Tribe in 1934. Confederated Tribes, 75 F. Supp.
3d at 400. Thus, the IRA’s second definition does not
overcome the ambiguity we see in the first definition.

     We move on to legislative history, which similarly does
not provide any clarity on when recognition must occur or
what it entails. The Senate Committee on Indian Affairs
discussed how to define “Indian” throughout April and May
of 1934, and did so in contradictory ways. One exchange
between Senator Elmer Thomas and Commissioner of Indian
Affairs John Collier suggested the IRA was being crafted
expansively, to “throw[] open Government aid to those
rejected Indians.” To Grant to Indians Living Under Federal
Tutelage the Freedom to Organize for Purposes of Local Self-
Government and Economic Enterprises: Hearing on S. 2755
and S. 3645 Before the S. Comm. on Indian Affairs, 73 Cong.
80 (1934) [hereinafter Subcommittee Hearing].             Other
Senators expressed concern about whether individuals might
evade the blood quantum requirement in the third definition
of Indian, covering persons of one-half or more Indian blood,
25 U.S.C. § 479, if they could show they were “members of
any recognized Indian tribe,” Subcommittee Hearing at 266.
To cabin eligibility, Chairman Wheeler said, “You would
have to have a limitation after the description of the tribe,”
after which Collier suggested inserting “now under Federal
jurisdiction,” after “recognized Indian tribe.” Subcommittee
Hearing at 266. The hearing then abruptly ended, leaving
only so much to glean from these words – certainly nothing
about when recognition must occur. At most, this history
reflects Congressional intent to limit what was a much
broader concept of recognition by some “jurisdictional”
connection to the government, even though, as discussed
later, nobody seemed to know what that jurisdictional
connection might be. While not telling us anything about any
time limitation on recognition, the legislative history at least
                              15
counters Appellants’ contention that “recognized Indian tribe”
was some established term of art unambiguously referring to a
tribe’s political status.

                              3.

     Proceeding to Chevron Step Two, we note that
Appellants raise claims under both Chevron and State Farm,
which in this case overlap. See EDWARDS, supra, at 217 (“In
[some] situations, what is ‘permissible’ under Chevron is also
reasonable under State Farm.”) (quoting Arent v. Shalala, 70
F.3d 610, 616 n.6 (D.C. Cir. 1995)). Ultimately, we defer to
Interior’s interpretation of the statute. Citizens Exposing
Truth, 492 F.3d at 465. Consistent with Justice Breyer’s
concurrence in Carcieri, it was not unlawful for the Secretary
to conclude that a “tribe need only be ‘recognized’ as of the
time the Department acquires the land into trust.” J.A. 255.

     Appellants disagree on account of what they allege is
inconsistent agency interpretation of the IRA. See Alabama
Educ. Ass’n v. Chao, 455 F.3d 386, 392 (D.C. Cir. 2006)
(“When an agency adopts a materially changed interpretation
of a statute, it must in addition provide a ‘reasoned analysis’
supporting its decision to revise its interpretation.” (quoting
Motor Vehicles Mfrs. Ass’n of U.S., Inc. v. State Farm Mut.
Auto. Ins. Co., 463 U.S. 29, 57 (1983))). Appellants believe
four things in particular prove their point: 1) a 1976
Department decision regarding the Stillaguamish Tribe; 2) a
1980 decision in Brown v. Commissioner of Indian Affairs by
the Interior Board of Indian Appeals, 8 IBIA 183 (1980); 3) a
1994 Department letter to the House Committee on Natural
Resources; and 4) a 2015 Department decision regarding the
Mashpee Wampanoag Tribe. We reject the inferences
Appellants would have us draw from each of these
documents, none of which shows a “materially changed
                               16
[agency] interpretation” of the IRA. Alabama Educ. Ass’n,
455 F.3d at 392. Rather, “administrative practice suggests
that the Department has [already] accepted th[e] possibility”
that “[t]he statute . . . imposes no time limit upon
recognition.”    Carcieri, 555 U.S. at 398 (Breyer, J.,
concurring).

     The Stillaguamish Tribe’s path to qualifying for IRA
benefits actually shows that the IRA does not limit the
benefits it confers only to tribes recognized as of 1934.
Appellants point to Interior’s 1976 decision denying the
tribe’s request to take certain land into trust, but that was not
the end of the story. What they fail to mention is that Interior
reconsidered this decision just a few years later, in 1980. In
so doing, it concluded the opposite – that the Stillaguamish
did in fact “constitute a tribe for purposes of the IRA.” J.A.
527. “It is irrelevant,” explained the Department, “that the
United States was ignorant in 1934 of the rights of the
Stillaguamish.” J.A. 526 (emphasis added). The government
even went so far as to say that it did not matter that it had “on
a number of occasions . . . taken the position that the
Stillaguamish did not constitute a tribe.” J.A. 527. Indeed,
there are several instances throughout history where the
United States initially has determined that a tribe “had long
since been dissolved,” only to correct this misapprehension
later in time. See Carcieri, 555 U.S. at 398-99 (Breyer, J.,
concurring). The Stillaguamish experience is therefore
consistent with Interior’s position vis-à-vis the Cowlitz.

     The Brown v. Commissioner of Indian Affairs decision is
of no greater help to Appellants. 8 IBIA 183 (1980). There,
the Interior Board of Indian Appeals confronted whether the
appellant’s Cowlitz nephew could receive a gift deed of a
portion of his uncle’s allotment on the Quinault Tribe
reservation. To receive the gift, the nephew had to be an
                              17
“Indian” under the IRA. Id. at 184-85. The Board first
considered if the nephew qualified on account of his inclusion
on the official census roll of the “Indians of the Quinault
Reservation” back “when the IRA was passed.” Id. at 187.
The uncle argued that the nephew’s prior membership in that
group provided the necessary statutory hook because the
group had been “under Federal jurisdiction” in 1934. See id.
at 188. The Board, however, declined “to dwell on the import
of th[a]t phrase.” Id. It was furthermore unconvinced that the
“Indians of the Quinault Reservation” were “one and the
same” as the present-day, federally recognized Quinault
Tribe, and so rejected the uncle’s argument. Id. at 188.

     The Board therefore did not offer a contrary
interpretation of “recognized” in its discussion of the
nephew’s membership in the “Indians of the Quinault
Reservation.” Nor did the Board elsewhere hold that the IRA
requires Cowlitz recognition in 1934. See Grand Ronde Br.
13. “[I]n the absence” back in 1980 “of any evidence that
[the nephew] was or is now a member of any other federally
recognized tribe,” id. at 190, the Board was left to uphold the
conveyance under the IRA’s second definition, see id.
Knowing what we know now, post-2002, the conclusion that
the nephew could not rely on his membership in the as-yet
unrecognized Cowlitz Tribe is unremarkable.            This is
especially true in light of the Stillaguamish opinion, issued
that same year, which confirms that the government has
sometimes mistakenly taken a position that an Indian group
does not constitute a tribe.

     We can next dismiss outright the idea that Interior offered
a contrary position in a 2015 record of decision to the
Mashpee Wampanoag Tribe. See Grand Ronde Br. 13-14.
Appellants’ reliance on that decision is odd, given that
Interior expressly said “there is no temporal limitation on the
                                18
term ‘recognized’ and therefore, recognition in 1934 is not
required.” J.A. 4553 n.237.

      Lastly, we find no merit in Appellants’ remaining
argument based on the inclusion of the year, 1934, in brackets
in one sentence of a 1994 letter to the House Committee on
Natural Resources. See J.A. 4636 (paraphrasing the first
definition of “Indian” as including “all persons of Indian
descent who are members of any recognized [in 1934] tribe
under Federal jurisdiction”). We fail to glean from those
brackets or the letter any interpretation of the statute, let alone
a departure from past agency interpretation; instead, the
Assistant Secretary was responding to a request “to provide a
list of nonhistoric Indian tribes.” J.A. 4634. Even when the
Supreme Court adjudicated the meaning of the the IRA’s first
definition of “Indian” in Carcieri, it was unswayed by the
persuasive authority of precisely this type of parenthetical.
Compare United States v. John, 437 U.S. 634, 650 (1978)
(writing that the IRA defined “Indian” in part as “all persons
of Indian descent who are members of any recognized [in
1934] tribe now under Federal jurisdiction”), with Brief of
Petitioner at 25-26, Carcieri v. Salazar, 555 U.S. 379 (2009)
(No. 07-526) (advocating that “[t]he bracketed phrase ‘in
1934’ [in United States v. John] . . . reflects the Court’s
understanding that the word ‘now’ restricts the operation of
the IRA to tribes that were federally recognized and under
federal jurisdiction at the time of enactment”), and Carcieri,
555 U.S. at 381-96 (nowhere citing United States v. John in
holding that “now under Federal jurisdiction” is restricted to
1934.).

     As shown above, Interior’s interpretation was reasonable.
Neither the agency decisions pointed to by Appellants, nor the
parenthetical from the 1994 letter – nor United States v. John,
for that matter – persuade us otherwise, and we are bound to
                               19
defer to the Board’s reasonable interpretation of the statute it
is charged to administer. UC Health v. NLRB, 803 F.3d 669,
681 (D.C. Cir. 2015).

                               B.

    The Secretary’s authority to take land into trust, as
mentioned, is limited to “recognized Indian tribe[s] now
under Federal jurisdiction,” 25 U.S.C. § 479, which leads
Appellants also to challenge the Secretary’s determination on
what is required by the IRA’s jurisdictional requirement.

     The Secretary interpreted “now under Federal
jurisdiction” to require a two-part inquiry. J.A. 260. First, the
Secretary considers:

       whether there is a sufficient showing in the
       tribe’s history, at or before 1934, that it was
       under federal jurisdiction, i.e., whether the
       United States had in 1934 or at some point in
       the tribe’s history prior to 1934, taken an
       action or series of actions – through a course
       of dealings or other relevant acts for or on
       behalf of the tribe or in some instance tribal
       members – that are sufficient to establish, or
       that generally reflect federal obligations,
       duties, responsibility for or authority over the
       tribe by the Federal Government.

J.A. 260-61. The second part of the test takes into account
whether the Federal-jurisdiction status remained intact in
1934. J.A. 261.

    Applying this test, the Secretary detailed the
government’s course of dealings with the Cowlitz dating from
                              20
failed treaty negotiations at the 1855 Chehalis River Treaty
Council, J.A. 263, to acknowledgment and communication
with Cowlitz chiefs in the late 19th century, J.A. 264, to
government provision of services into the 1900s, J.A. 265, to
supervision in the 1920s by the local Taholah Agency,
J.A. 265, to organization and claims efforts leading up to the
ICC award, J.A. 266, to allotment activities, J.A. 267-68.
Another “important action by the Federal Government
evidencing the Tribe was under federal jurisdiction in 1934”
was Interior’s approval of an attorney contract for the Tribe in
1932, pursuant to a statute that required contracts between
Indian tribes and attorneys be approved by the Commissioner
of Indian Affairs and Secretary. J.A. 269. Furthermore, the
Secretary explicitly rejected arguments relating to the 2005
NIGC Restored Lands Opinion, which discussed the lack of a
government-to-government relationship with the Tribe, as
conflating the modern, political concept of recognition with
that used in the IRA, which was closer to an “ethnological and
cognitive” concept. J.A. 270-71. In any event, the Secretary
explained, “recognition is not the inquiry before us. Rather, it
is the concept of federal jurisdiction that is addressed.”
J.A. 270.

     Appellants urge that the phrase, “under Federal
jurisdiction” is unambiguous, but we disagree. Congress
nowhere in the statute gave further meaning to these words.
Moreover, “jurisdiction” is a term of extraordinary breadth.
Indian tribes are independent sovereigns, but at the same time
“domestic dependent nations,” Cherokee Nation v. Georgia,
30 U.S. 1, 2 (1831), and subject to the “plenary and
exclusive” authority of Congress, United States v. Lara, 541
U.S. 193, 200 (2004). As the government notes, due to
Congress’s plenary powers, every Indian tribe could be
considered “under Federal jurisdiction” in some sense.
See Gov’t Br. 51. As already discussed, the legislative history
                               21
provides no further clues, except that the jurisdictional nexus
was meant as some kind of limiting principle.
See Subcommittee Hearing at 266. Precisely how it would
limit the universe of recognized tribes is unclear; Assistant
Solicitor of the Interior Felix Cohen contemporaneously
described the Senate bill as including the term, “‘now under
Federal jurisdiction’, whatever that may mean.” S.A. 3
(emphasis added). Interior correctly predicted at the time that
the phrase was “likely to provoke interminable questions of
interpretation.” J.A. 398 (agency analysis of differences
between House and Senate bills, 1934). Indeed it has. We
easily conclude that the phrase is ambiguous.

     The Secretary’s two-part test is furthermore reasonable.
It makes sense to take treaty negotiations into account, as one
of several factors reflecting authority over a tribe, even if they
did not ultimately produce agreement. This is all the more so
given the context within which the particular negotiations at
issue occurred. The Cowlitz refused to sign an 1855 land
cession treaty proposed at the Chehalis River Treaty Council,
J.A. 625, whereby Governor Stevens of the Washington
Territory and other federal agents sought to move the Cowlitz
to a reservation on the Pacific Coast, J.A. 660-68. The
Cowlitz resisted relocation and refused the treaty, J.A. 667,
but years later the United States offered the Cowlitz’s land for
sale to settlers without compensation anyway, J.A. 498. As
the District Court explained, the fact that the government
nevertheless took the Cowlitz land even after the tribe resisted
the treaty corroborates that the government treated the
Cowlitz as under its jurisdiction.

     We are not persuaded that the Secretary’s interpretation
is unreasonable for failure to require a formal, government-to-
government relationship carried out between the tribe and the
highest levels of the Interior Department. See Clark County
                              22
Br. 24; Grand Ronde Br. 28 (“[T]he existence of a
government-to-government relationship is the sine qua non of
federal jurisdiction.”). The statute does not mandate such an
approach, which also does not follow from any ordinary
meaning of jurisdiction.            Whether the government
acknowledged federal responsibilities toward a tribe through a
specialized, political relationship is a different question from
whether those responsibilities in fact existed. And as the
Secretary explained, we can understand the existence of such
responsibilities sometimes from one federal action that in and
of itself will be sufficient, and at other times from a “variety
of actions when viewed in concert.” J.A. 261. Such
contextual analysis takes into account the diversity of kinds of
evidence a tribe might be able to produce, as well as evolving
agency practice in administering Indian affairs and
implementing the statute. It is a reasonable one in light of the
remedial purposes of the IRA and applicable canons of
statutory construction.

     Appellants make several additional arguments urging that
the Secretary applied the two-part test in an arbitrary and
capricious manner. Appellants maintain that the Cowlitz
were “terminated” as a tribe as of 1934, which is the antithesis
of being under federal jurisdiction, and that “the Secretary did
not even address” this fact. Grand Ronde Br. 26. Appellants
further believe that the Tribe conceded that they had been
terminated before the NIGC, while advocating that it met the
restored-lands exception to the IGRA, and that the
Commission accepted this concession.

    This version of events is somewhat of a
mischaracterization. First, the Secretary did consider whether
the Cowlitz were previously terminated, and found “no clear
evidence” that the government terminated the Cowlitz, or that
the tribe otherwise lost that status. J.A. 264. Second, the
                              23
NIGC opinion is of little value when it comes to this
particular inquiry. In order to meet the restored-lands
exception – a requirement of the IGRA, not the IRA – the
Commission interpreted the IGRA to require, inter alia, a
period of non-recognition by the government. J.A. 1362
(citing Grand Traverse Band of Ottawa & Chippewa Indians
v. Office of U.S. Atty. for the W. Div. of Mich., 369 F.3d 960,
967 (6th Cir. 2004)). So, whereas Appellants point to a 1933
quotation within the NIGC opinion, where Commissioner
Collier said the Cowlitz were “no longer in existence as a
communal entity,” Grand Ronde Br. 24-25 (citing J.A. 1364),
that sentiment goes to the government’s mistaken belief at the
time that the Cowlitz had been absorbed into the greater
population. That error is consistent with the NIGC’s
conclusion that “the historical evidence establishes that the
United States did not recognize the Cowlitz Tribe as a
governmental entity from at least the early 1900s until 2002.”
J.A. 1363 (emphasis added). It is a conclusion about
recognition – not whether the Tribe was under Federal
jurisdiction. Finally, neither the Secretary nor this Court is
bound by the Cowlitz’s previous position before the NIGC.
The Cowlitz used the term, “de facto termination,” J.A. 1289,
but essentially argued that the government failed to recognize
it for a period of time, which is true.

     The only additional argument we need address is the
assertion that the ROD is contrary to the agency’s history of
“consistently” finding the Cowlitz were not under federal
jurisdiction in 1934. Grand Ronde Br. 30. Appellants focus
on yet another lone sentence within an agency technical report
produced during the federal acknowledgment process. See
J.A. 1076 (discussing documents that purportedly showed the
Cowlitz were not a “reservation tribe under Federal
jurisdiction or under direct Federal supervision”). We think
this statement reflects a narrower and dated understanding
                               24
that equated land and direct supervision with jurisdiction. But
the Secretary explained in the ROD that jurisdiction can be
shown in more ways than that, see J.A. 260-63, and
adequately documented the dealings that evidenced
jurisdiction in 1934, see J.A. 267 (relying on a March 16,
1934 instruction from the Taholah agency to place Cowlitz
Indians on the census roll for the Quinault Reservation);
J.A. 269 (citing evidence of the agency granting “allotments
[on the Quinault Reservation] to eligible Cowlitz Indians
during the period from 1905 to 1930”); J.A. 269 (referencing
agency approval of an attorney contract that was in the name
of “the Cowlitz Tribe or Band of Indians”). At the end of the
day, there is a large and complex record of Interior
interactions with the Cowlitz for almost a century. The
erroneous assumption that the Cowlitz no longer existed may
have colored lone statements, when taken out of context,
touching on aspects of jurisdiction over the Tribe. However,
after reviewing the record in its entirety, we are confident that
the Secretary reasonably determined the contacts between the
United States and the Cowlitz from 1855 through 1934
satisfied part one of the two-part test, and that those contacts
remained intact despite what was at times the agency’s
equivocal exercise of its authority and responsibilities.

                               C.

     Appellants next dispute the Secretary’s determination
that the Cowlitz parcel met the initial-reservation exception
under the IGRA, so as to permit gaming on that land.

     To recall, the IGRA’s initial-reservation exception from
its ban against gaming on Indian lands includes those lands
taken into trust as “the initial reservation of an Indian tribe
acknowledged by the Secretary under the Federal
acknowledgment process.” 25 U.S.C. § 2719(b)(1)(B)(ii).
                              25
Interior regulations require a tribe seeking to come within that
exception to show, inter alia, that the land in question is
“within an area where the tribe has significant historical
connections.” 25 C.F.R. § 292.6(d) (emphasis added). This is
in contrast to the restored-lands exception, which requires at
least “a significant historical connection to the land” itself.
Id. § 292.12 (b) (emphasis added). A tribe can show
significant historical connections by “demonstrat[ing] by
historical documentation the existence of the tribe’s villages,
burial grounds, occupancy or subsistence use in the vicinity of
the land.” Id. § 292.2. The Secretary has interpreted
“vicinity” in both the initial-reservation and restored-lands
context to mean “those circumstances” of use and occupancy
“lead[ing] to the natural inference that the tribe also made use
of the” parcel in question.” J.A. 292; see also J.A. 4518,
4534.

     The Secretary determined that the Cowlitz met the initial-
reservation exception after reviewing a number of historical
sources, including those relied on by the ICC and the
government      during     the    federal    acknowledgment
determination. The Secretary identified evidence of Cowlitz
use or occupancy three miles northwest of the Cowlitz parcel,
J.A. 295 (lodges and about 100 “Kowalitsk”), ten miles south,
J.A. 296 (trading presence), and less than three miles north
from the Cowlitz Parcel, J.A. 300-01 (Cowlitz boatmen), as
well as “exclusive use and occupancy . . . within 14 miles,”
J.A. 298 (ICC decision). The ROD further relied on signs of
a major Cowlitz battle in the 1800s less than three miles from
the parcel, J.A. 299, and, only six miles from the parcel,
hunting by the Cowlitz Indian Zack, who also assisted settlers
during the 1855-1856 Indian war, J.A. 300. The record also
includes documentation of the Tribe’s presence at Fort
Vancouver, J.A. 297, 301, which is south of the city of
Vancouver, Washington, which itself is south of the land in
                               26
question. All of this provided sufficient “historical evidence
of occupancy and use by the Cowlitz of lands in the vicinity
of the Cowlitz Parcel,” and “significant historical connections
to the Cowlitz Parcel.” J.A. 302.

     Appellants attack “[t]he Secretary’s IGRA ruling [as]
constitut[ing] the worst sort of ad hoc decision-making.”
Grand Ronde Br. at 42. Specifically, they allege the
Secretary: 1) used the wrong standard; 2) failed to recognize
that, under the right standard, the initial-reservation test
requires significant historical connections “to the parcel
itself,” which the Cowlitz cannot show; and 3) departed from
agency precedent.

     Appellants base their first two objections on two
perceived ambiguities within the ROD. At times the
Secretary used language indicating not just that the Cowlitz
had a demonstrable presence within an area of significant
historical connection to the parcel, but that the evidence
showed a connection to the parcel itself. Compare J.A. 291
(“We determine that the Cowlitz Tribe has significant
historical connections to the land in the vicinity of the Cowlitz
Parcel.”), with J.A. 303 (“The key question is whether the
historic Cowlitz Indians had significant historical connections
with the Cowlitz Parcel.”). Second, although the Secretary
cited the Scotts Valley Opinion, explaining that whether a
tribe’s use and occupancy occurred “within the vicinity” of
the land at issue asks whether the circumstances “lead to the
natural inference that the tribe also made use of the parcel in
question,” J.A. 292 (internal quotation marks omitted), the
Secretary did not again use the words, “natural inference,” in
explaining how the numerous pieces of evidence supported
the ROD’s conclusion that the parcel fulfilled the IGRA’s
regulatory requirements.
                              27
     Seeing as the Secretary ultimately “conclude[d] that the
Tribe has significant historical connections with the Cowlitz
Parcel,” J.A. 302, any error the Secretary may have made in
that regard did not amount to reversible error, see 5 U.S.C.
§ 706 (“[D]ue account shall be taken of the rule of prejudicial
error.”). We are unconvinced that the Secretary used the
wrong standard. If anything, the Secretary used the correct
standard but found more than what was necessary for the
initial-reservation exception. To be clear, contrary to the
interpretation pressed by Grand Ronde, this exception does
not mandate that historical documentation implicate the actual
land where gaming will take place. The regulation provides
that the Cowlitz had only to show that the parcel was “within
an area where the tribe has significant historical connections.”
25 C.F.R. § 292.6(d) (emphasis added).              Indeed, the
regulation’s breadth comports with the agency’s rejection of
various, strict forms of the test suggested at the time of the
regulation’s adoption, which the agency feared might “create
too large a barrier to tribes in acquiring lands.” Gaming on
Trust Lands Acquired After October 17, 1988, 73 Fed. Reg.
29,354, 29,360 (May 20, 2008); see also Citizens Exposing
Truth, 492 F.3d at 467 (“IGRA’s [initial-reservation]
exception ‘ensur[es] that tribes lacking reservations when
IGRA was enacted are not disadvantaged relative to more
established ones.’”) (quoting City of Roseville, 348 F.3d at
1030). Thus, the agency’s interpretation of its regulation was
in line with its intent at the time of promulgation, and any
ambiguity in the language used by the agency as it
exhaustively analyzed evidence dating back to the early 1800s
only shows the ROD went above and beyond fulfilling the
regulatory requirements. Cf. PDK Labs. Inc. v. U.S. D.E.A.,
362 F.3d 786, 799 (D.C. Cir. 2004) (“If the agency’s mistake
did not affect the outcome, if it did not prejudice the
petitioner, it would be senseless to vacate and remand for
reconsideration.”).
                              28
     Moving on, Appellants urge that the ROD broke from
past precedent, but the gist of their argument is really that
they disagree with the Secretary’s finding that the record
establishes “significant” connections to the parcel. See Clark
County Br. 47 (“[T]he Secretary has required connections
based on subsistence use and occupancy to be enduring,
substantial, and non-speculative.” (emphasis deleted)); Grand
Ronde Br. 36 (“[N]ot just any historical connections will
do.”). There is no “sharp break” from the opinions regarding
the Scott’s Valley Band of Pomo Indians, Grand Ronde
Br. 39, the Guidiville Band of Pomo Indians, Clark County
Br. 50-51 & n.20, or any others, see Grand Ronde Br. 40 n.18.
To the extent Appellants think this precedent shows Interior
required a higher quantum of evidence in previous cases,
those were restored-lands opinions, see J.A. 4303, 4336,
where a connection was made “often [to] the very heart of the
tribe’s territory.” Grand Ronde 39; see also 25 C.F.R.
§ 292.12(b) (necessitating “a significant historical connection
to the land” (emphasis added)).

     Appellants’ strongest argument is that the agency in an
opinion to the Guidiville Band said that documentation of a
trade route was insufficient to establish subsistence use
because “something more than evidence that a tribe merely
passed through a particular area is needed.” J.A. 4316. At
first glance, that is in contrast to the Cowlitz ROD, where
“[e]vidence of trade and trade routes . . . [wa]s a key
consideration.” J.A. 298. The Cowlitz ROD does not stop
there, however, but continues to distinguish the Guidiville
Opinion by explaining that it had not previously “conclude[d]
that activities associated with a trade route or trading
activities in general can never constitute evidence of
significant historical connections.” J.A. 299. “[S]uch
activities have to be substantial enough to be more than ‘a
transient presence in the area,’” explained the Secretary,
                              29
J.A. 299, which is the same as its prior interpretation of the
regulation, see J.A. 4316 (requiring in the Guidiville Opinion
“something more than a transient presence in an area”).

    The ROD is supported by substantial evidence amply
showing that Interior found the Cowlitz parcel to be within a
broader area of historical significance to the Tribe. J.A. 292-
302. The decision is not otherwise arbitrary or capricious,
and thus we find no merit in Appellants’ challenges on this
front.

                              D.

    The Clark County Appellants alone bring these next
claims stemming from the Tribe’s membership growth in the
time since its federal acknowledgment application. We reject
them all.

     In April 2006, Interior issued a DEIS for the casino. The
agency subsequently received comments requesting that it
provide the tribe’s business plan, which is required as part of
the tribe’s fee-to-trust application package. See 25 C.F.R.
151.11(c) (“Where land is being acquired for business
purposes, the tribe shall provide a plan which specifies the
anticipated economic benefits associated with the proposed
use.”). The plan showed the Tribe had 3,544 members. It also
stated the Tribe would require approximately $113 million
annually for its “unmet needs,” or, in other words, to fund
government infrastructure, programs, and services. The
Secretary appended the plan to the FEIS, which included the
$113 million figure from the plan in the FEIS Purpose and
Need statement.

    Appellants protest that the Tribe’s new membership level
from the business plan represents a dramatic increase from
                               30
1,482 members in 2002, when the Cowlitz were first federally
acknowledged. See Clark County Br. 27-28. Under IRA
regulation 25 C.F.R. § 83.12(b) (1994), 7 the Cowlitz had
submitted a list of members as part of the federal
acknowledgment process, which became its official “base
roll” for federal funding and other purposes. That regulation
also provides that additions to the roll must meet certain
criteria, such as “maintaining significant social and political
ties with the tribe,” see Clark County Mot. Summ. J. 25
(citing 25 C.F.R. § 83.12(b) (1994)), and so Clark County
believes the agency had a duty to verify the membership
increase, see Clark County Br. 27-28.           Clark County
additionally argues that the agency had a duty under NEPA’s
implementing regulations to verify the Tribe’s self-reported
unmet economic needs. Clark County Br. 35-39. Appellants’
concern in that regard relates back to the agency’s
consideration of the range of reasonable alternatives, see
Confederated Tribes, 75 F. Supp. 3d at 420-21; Interior had
originally identified nineteen possible project locations, but
eliminated five locations that were north of the parcel as too
inconvenient to the Seattle and Portland markets to
“adequately meet the economic objectives and needs of the
Tribal government,” id. at 420 (citing J.A. 2805).

     We first reject any claim regarding 25 C.F.R. § 83.12(b)
as forfeited. Clark County never raised to the agency a duty
to verify membership enrollment pursuant to this regulation.
The best Appellants can point to are letters expressing the
County’s concern to the agency about the business plan and
the Tribe’s unmet needs in reference to the NEPA process.

7
  In 2015, Interior updated and revised the Part 83 regulations,
eliminating this particular “base roll” limitation provision. See
Federal Acknowledgment of American Indian Tribes, 80 Fed. Reg.
37,862, 37,885 (July 1, 2015).
                               31
See J.A. 2144-46 (letter to BIA submitting supplemental
comments to the DEIS); J.A. 2375 (letter to Interior arguing
that the tribe is using inflated member statistic in its “Business
Plan to inflate its tribal needs to constrain BIA review and
short circuit the NEPA process”); see also Clark County
Br. 30 (citing to instances in the record where it framed the
expansion issue in terms of NEPA reasonable alternatives).
Not only did Clark County fail to invoke Section 83.12(b) in
express terms, but it was not “necessarily implicated” in
discussion of an entirely different statutory scheme.
NetworkIP, LLC v. FCC, 548 F.3d 116, 122 (D.C. Cir. 2008).
And despite referencing NEPA in these letters, Appellants fail
to point us to any of their comments to the FEIS raising
concerns about Cowlitz membership levels. This directly
undercuts their claim that the Secretary failed to address
questions about the Tribe’s expanded enrollment. While
some comments responding to the FEIS referenced the
Tribe’s unmet needs figure, as opposed to membership levels,
see, e.g., J.A. 3381, 3413, the Secretary fully addressed all
questions about the business plan actually raised before the
agency, see J.A. 191 (determining agency review of a
“Tribe’s internal economic planning strategy document” to
“be inappropriate and contrary to federal Indian policies
encouraging tribal sovereignty, self-determination and self-
governance”).

     We are similarly unpersuaded that the Secretary had an
obligation under NEPA regulation 40 C.F.R. § 1506.5(a) to
verify that the Cowlitz’s unmet needs report was accurate.
See Clark County Br. 35-39. That regulation provides that
“[i]f an agency requires an applicant to submit environmental
information for possible use by the agency in preparing an
environmental impact statement . . . [t]he agency shall
independently evaluate the information submitted and shall be
responsible for its accuracy.”     Id. § 1506.5(a) (emphasis
                             32
added). Neither the annual unmet needs figure complained of
here, nor the membership numbers that purportedly inflated
the Tribe’s unmet needs, are environmental in nature. It may
be the case that Section 1506.5(a) might in other
circumstances apply to some kind of information that is
simultaneously socioeconomic and environmental, as
Appellants argue. See Clark County Br. 37. But at least as
presented here, Clark County’s quarrel is that the agency’s
failure to do its own investigation resulted in excluding from
consideration reasonable alternatives located farther away
from competing casino interests. See Clark County Br. 38;
see also J.A. 3366 (lamenting the economic impact of the
“emergence of a tribal casino on the outskirts of” La Center,
Washington). That is the gravamen of this particular
complaint, which we are not convinced is appropriately
pursued under Section 1506.5. As Clark County did not
challenge on any other grounds the decision to exclude certain
allegedly reasonable alternatives from the FEIS, see
Confederated Tribes, 75 F. Supp. 3d at 419-20, we have no
occasion to rule on those issues. Clark County ultimately
cannot prevail in any of its claims related to the Tribe’s
membership or business plan.

                             ***

     For all of the foregoing reasons, we affirm the judgment
of the District Court in its entirety.
                                                   So ordered.
