                    FOR PUBLICATION
  UNITED STATES COURT OF APPEALS
       FOR THE NINTH CIRCUIT

SAN LUIS OBISPO MOTHERS FOR               
PEACE; SANTA LUCIA
CHAPTER OF THE SIERRA CLUB; PEG
PINARD,
                      Petitioners,                No. 03-74628
                                                    NRC No.
                                          
PACIFIC GAS AND ELECTRIC
COMPANY,                                           CLI-03-01;
                       Intervenor,                 CLI-02-23
                v.                                 OPINION
NUCLEAR REGULATORY COMMISSION;
UNITED STATES OF AMERICA,
                     Respondents.
                                          
          On Petition for Review of an Order of the
              Nuclear Regulatory Commission

                   Argued and Submitted
         October 17, 2005—San Francisco, California

                        Filed June 2, 2006

     Before: Stephen Reinhardt and Sidney R. Thomas,
     Circuit Judges, and Jane A. Restani,* Chief Judge,
         United States Court of International Trade

                   Opinion by Judge Thomas




   *The Honorable Jane A. Restani, Chief Judge, United States Court of
International Trade, sitting by designation.

                                6063
               SAN LUIS OBISPO MOTHERS v. NRC               6067


                          COUNSEL

Diane Curran, Harmon, Curran, Spielberg & Eisenberg,
L.L.P., Washington, D.C., for the petitioners.

Charles E. Mullins, United States Nuclear Regulatory Com-
mission, Washington, D.C., for the respondents.

David A. Repka, Winston & Strawn, L.L.P., Washington,
D.C., for respondent-intervenor PG&E.

Sheldon L. Trubatch, Esq., Offices of Robert K. Temple,
Esq., Chicago, Illinois, for amicus San Luis Obispo County.

Kevin James, California Department of Justice, Oakland, Cal-
ifornia, for amicus States of California, Massachusetts, Utah
and Washington.

Jay E. Silberg, Shaw Pittman, L.L.P., Washington, D.C., for
amicus Nuclear Energy Institute.


                          OPINION

THOMAS, Circuit Judge:

   This case presents the question, inter alia, as to whether the
likely environmental consequences of a potential terrorist
6068           SAN LUIS OBISPO MOTHERS v. NRC
attack on a nuclear facility must be considered in an environ-
mental review required under the National Environmental
Policy Act. The United States Nuclear Regulatory Commis-
sion (“NRC”) contends that the possibility of a terrorist attack
on a nuclear facility is so remote and speculative that the
potential consequences of such an attack need not be consid-
ered at all in such a review. The San Luis Obispo Mothers for
Peace and other groups disagree and petition for review of the
NRC’s approval of a proposed Interim Spent Fuel Storage
Installation. We grant the petition in part and deny it in part.

                               I

   The NRC is an independent federal agency established by
the Energy Reorganization Act of 1974 to regulate the civilian
use of nuclear materials. Intervenor Pacific Gas and Electric
Company (“PG&E”) filed an application with the NRC under
10 C.F.R. Part 72 for a license to construct and operate an
Interim Spent Fuel Storage Installation (“Storage Installation”
or “ISFSI”) at PG&E’s Diablo Canyon Power Plant (“Diablo
Canyon”) in San Luis Obispo, California. The NRC granted
the license. The question presented by this petition for review
is whether, in doing so, the NRC complied with federal stat-
utes including the National Environmental Policy Act of 1969
(“NEPA”), 42 U.S.C. §§ 4321-4437, the Atomic Energy Act
of 1954 (“AEA”), 42 U.S.C. §§ 2011-2297g, and the Admin-
istrative Procedure Act (“APA”), 5 U.S.C. §§ 551-706.

   NEPA establishes a “national policy [to] encourage produc-
tive and enjoyable harmony between man and his environ-
ment,” and was intended to reduce or eliminate environmental
damage and to promote “the understanding of the ecological
systems and natural resources important to” the United States.
Dept. of Transp. v. Pub. Citizen, 541 U.S. 752, 756 (2004)
(quoting 42 U.S.C. § 4321). The Supreme Court has identified
NEPA’s “twin aims” as “plac[ing] upon an agency the obliga-
tion to consider every significant aspect of the environmental
impact of a proposed action[, and] ensur[ing] that the agency
              SAN LUIS OBISPO MOTHERS v. NRC                 6069
will inform the public that it has indeed considered environ-
mental concerns in its decisionmaking process.” Baltimore
Gas & Elec. Co. v. Natural Res. Def. Counsel, Inc., 462 U.S.
87, 97 (1983).

   Rather than mandating particular results, NEPA imposes on
federal agencies procedural requirements that force consider-
ation of the environmental consequences of agency actions.
Pub. Citizen, 541 U.S. at 756. At NEPA’s core is the require-
ment that federal agencies prepare an environmental impact
statement (“EIS”), or:

    include in every recommendation or report on pro-
    posals for legislation and other major Federal actions
    significantly affecting the quality of the human envi-
    ronment, a detailed statement by the responsible offi-
    cial on—(i) the environmental impact of the
    proposed action, (ii) any adverse environmental
    effects which cannot be avoided should the proposal
    be implemented, (iii) alternatives to the proposed
    action, (iv) the relationship between local short-term
    uses of man’s environment and the maintenance and
    enhancement of long-term productivity, and (v) any
    irreversible and irretrievable commitments of
    resources which would be involved in the proposed
    action should it be implemented.

Id. at 757 (quoting 42 U.S.C. § 4332(2)(C)).

   As an alternative to the EIS, an agency may prepare a more
limited environmental assessment (“EA”) concluding in a
“Finding of No Significant Impact” (“FONSI”), briefly pre-
senting the reasons why the action will not have a significant
impact on the human environment. Id. at 757-58 (citing 40
C.F.R. §§ 1501.4(e), 1508.13). If, however, the EA does not
lead to the conclusion that a FONSI is warranted, the agency
remains obligated to prepare an EIS. Id. at 757.
6070          SAN LUIS OBISPO MOTHERS v. NRC
   While NEPA requires the NRC to consider environmental
effects of its decisions, the AEA is primarily concerned with
setting minimum safety standards for the licensing and opera-
tion of nuclear facilities. The NRC does not contest that the
two statutes impose independent obligations, so that compli-
ance with the AEA does not excuse the agency from its
NEPA obligations. The AEA lays out the process for consid-
eration of the public health and safety aspects of nuclear
power plant licensing, and requires the NRC to determine
whether the licensing and operation of a proposed facility is
“in accord with the common defense and security and will
provide adequate protection to the health and safety of the
public.” 42 U.S.C. § 2232(a).

   The NRC is not, however, required to make this determina-
tion without assistance; federal law provides a framework for
hearings on material issues that interested persons raise by
specific and timely petition. 42 U.S.C. § 2239(a); 10 C.F.R.
§§ 2.308-.348; 5 U.S.C. §§ 551-706. The initial hearing is
held before a three-person Atomic Safety and Licensing
Board (“Licensing Board”). 10 C.F.R. § 2.321. The Licensing
Board’s findings and decision constitute the agency’s initial
determination, although a party may file a petition for review
with the Commission within 15 days of the Licensing Board’s
decision. 10 C.F.R. § 2.341. If the petition is granted, the
Commission specifies the issues to be reviewed and the par-
ties to the review proceedings, 10 C.F.R. § 2.341(c)(1), and
renders a final decision. 10 C.F.R. § 2.344. A party may then
petition this court for review of the Commission’s final deci-
sion. 28 U.S.C. § 2344.

                              II

  With this general statutory background, we turn to the facts
underlying the petition for review. On December 21, 2001,
PG&E applied to the NRC pursuant to 10 C.F.R. Part 72 for
a license to construct and operate a Storage Installation at
Diablo Canyon. The Storage Installation would permit the
                  SAN LUIS OBISPO MOTHERS v. NRC                       6071
necessary and on-site storage of spent fuel, the byproduct of
the two nuclear reactors at that site. PG&E expects to fill its
existing spent fuel storage capacity at Diablo Canyon some-
time this year. Therefore, unless additional spent fuel storage
capacity is created, the Diablo Canyon reactors cannot con-
tinue to function beyond 2006.

   PG&E proposes to build a dry cask storage facility. The
basic unit of the storage system is the Multi-Purpose Canister
(“Canister”), a stainless steel cylinder that is filled with radio-
active waste materials and welded shut. The Canisters are
loaded into concrete storage overpacks that are designed to
permit passive cooling via the circulation of air. The storage
casks, or the filled Canisters loaded into overpacks, are then
placed on one of seven concrete pads. The Storage Installation
would house a total of 140 storage casks, 2 more than the 138
projected to be required for storage of spent fuel generated at
Diablo Canyon through 2025.

   On April 22, 2002, the NRC published a Notice of Oppor-
tunity for Hearing. Under the regulatory scheme, interested
parties could then request a hearing or petition for leave to
intervene. 10 C.F.R. § 2.309(a). A written hearing request,
which must contain the contentions the party wants litigated
at the hearing, will be granted if the petitioner has standing,
and has posed at least one admissible contention.1 Id.

  On July 19, 2002, the San Luis Obispo Mothers for Peace,
a non-profit corporation concerned with Diablo Canyon’s
  1
    In order to be admissible, a contention must: be set forth with particu-
larity, 10 C.F.R. § 2.309(f)(1); provide a specific statement of the disputed
issue of law or fact, 10 C.F.R. § 2.309(f)(1)(i); provide the basis for the
contention, 10 C.F.R. § 2.309(f)(1)(ii); demonstrate that the issue is within
the scope of the proceeding, 10 C.F.R. § 2.309(f)(1)(iii); demonstrate that
the issue is material to the findings the NRC must make, 10 C.F.R.
§ 2.309(f)(1)(iv); provide supporting references and expert opinions, 10
C.F.R. § 2.309(f)(1)(v); and provide sufficient information to show the
existence of a genuine issue of law or fact, 10 C.F.R. § 2.309(f)(1)(vi).
6072             SAN LUIS OBISPO MOTHERS v. NRC
local impact, the Sierra Club, a non-profit corporation con-
cerned with national environmental policy, and Peg Pinard, an
individual citizen, (collectively “Petitioners”) submitted a
hearing request and a petition to intervene, asserting conten-
tions for admission.

   In Licensing Board Proceeding LBP-02-23, 56 NRC 413
(“LBP 02-23”), the Atomic Safety and Licensing Board
addressed the admissibility of the July 19 petition’s five Tech-
nical and three Environmental Contentions.2 One Technical
Contention, TC-1, dealing with the state of PG&E’s finances,
was deemed admissible; the acceptance of at least one conten-
tion meant that the petition was granted. Although the Licens-
ing Board deemed two Environmental Contentions, EC-1,
dealing with the failure to address environmental impacts of
terrorist or other acts of malice or insanity, and EC-3, dealing
with the failure to evaluate environmental impacts of trans-
portation of radioactive materials3 inadmissible, the Licensing
Board nonetheless referred the final ruling as to the admissi-
bility of these two contentions to the NRC, “in light of the
  2
     Technical Contention Number One (“TC-1”) alleged Inadequate Seis-
mic Analysis. TC-2 alleged PG&E’s Financial Qualifications Are Not
Demonstrated. TC-3 alleged PG&E May Not Apply for a License for a
Third Party. TC-4 alleged Failure to Establish Financial Relationships
Between Parties Involved in Construction and Operation of Installation.
TC-5 alleged Failure to Provide Sufficient Description of Construction
and Operation Costs. Environmental Contention Number One (“EC-1”)
alleged Failure to Address Environmental Impacts of Destructive Acts of
Malice or Insanity. EC-2 alleged Failure to Fully Describe Purposes of
Proposed Action or to Evaluate All Reasonably Associated Environmental
Impacts and Alternatives. EC-3 alleged Failure to Evaluate Environmental
Impacts of Transportation.
   3
     Because the Storage Installation is not a permanent repository, this
contention assumes the eventual transport of the materials stored there to
a permanent site. Among the materials submitted to support the contention
were some dealing with possible terrorist or other malicious attacks on the
spent fuel while in transit. The ruling on the contention was “referr[ed]
. . . to the Commission to the extent terrorism and sabotage matters are
proffered in support of its admission.” 56 NRC at 453.
                 SAN LUIS OBISPO MOTHERS v. NRC                   6073
Commission’s ongoing ‘top to bottom’ review of the agency’s
safeguards and physical security programs.” 56 NRC at 448.

   In a memorandum and order, CLI-03-1, 57 NRC 1 (“CLI
03-01”), the NRC accepted the Licensing Board’s referral of
its decision to reject the environmental contentions related to
terrorism. Although the Commission affirmed the Licensing
Board’s rejection of the contentions, it based its decision on
a different rationale. The NRC relied on four prior decisions
in which it held that the NEPA does not require a terrorism
review.4 These decisions, most particularly Private Fuel Stor-
age, CLI-02-25, 56 NRC 340 (2002), outlined four reasons
for this holding: (1) the possibility of terrorist attack is too far
removed from the natural or expected consequences of agency
action to require study under NEPA; (2) because the risk of
a terrorist attack cannot be determined, the analysis is likely
to be meaningless; (3) NEPA does not require a “worst-case”
analysis; and (4) NEPA’s public process is not an appropriate
forum for sensitive security issues. The NRC concluded:

     Our decision today rests entirely on our understand-
     ing of NEPA and of what means are best suited to
     dealing with terrorism. Nonetheless, our conclusion
     comports with the practical realities of spent fuel
     storage and the congressional policy to encourage
     utilities to provide for spent fuel storage at reactor
     sites pending construction of a permanent repository.
     Storage of spent fuel at commercial reactor sites
     offers no unusual technological challenges. Indeed,
     it has been occurring at Diablo Canyon for many
  4
    Those cases include: Private Fuel Storage, L.L.C., CLI-02-25, 56 NRC
340 (2002) (Storage Installation); Duke Cogema Stone & Webster (Mixed
Oxide Fuel Fabrication Facility), CLI-02-24, 56 NRC 335 (2002); Domin-
ion Nuclear Connecticut, Inc. (Nuclear Power Station), CLI-02-27, 56
NRC 367 (2002); and Duke Energy Corp. (Nuclear Power Station), CLI-
02-26, 56 NRC 358 (2002). All four cases were decided on December 18,
2002.
6074             SAN LUIS OBISPO MOTHERS v. NRC
      years and will continue whether or not we license the
      proposed Installation.

57 NRC at 7.

   In September of 2002, prior to the NRC’s decision on the
first petition, Petitioners submitted a second petition, this time
requesting suspension of the Storage Installation licensing
proceeding pending comprehensive review of the adequacy of
Diablo Canyon’s design and operation measures for protec-
tion against terrorist attack and other acts of malice or insan-
ity. Unlike the July 19 petition, this one addressed security
measures for the entire Diablo Canyon complex, not merely
the Storage Installation. Petitioners explained that 10 C.F.R.
§ 2.335, which prohibits challenges to any NRC rule or regu-
lation in an adjudicatory proceeding involving initial or
renewal licensing, prevented the raising of contentions con-
testing the adequacy of NRC safety requirements protecting
against terrorist or other malicious attacks on the entire com-
plex in the July 19 Petition. Petitioners also stated that 10
C.F.R. § 72.32 prevented them from raising emergency plan-
ning contentions in the earlier petition. Thus, Petitioners
insisted that the second petition “d[id] not constitute a request
for rulemaking, nor . . . for enforcement action,” and instead
defined it, without reference to any particular hearing-
granting provision of the regulations, as “a request for actions
that are necessary to ensure that any licensing decision made
by the Commission with respect to the proposed Diablo Can-
yon Installation complies with the Commission’s statutory
obligations under the Atomic Energy Act.”

   In a memorandum and order, CLI-02-23, 56 NRC 230
(“CLI 02-23”), the NRC denied the September 2002 petition.
Because the petition did not, according to the NRC, “fit com-
fortably in any specific category, [the Commission] treat[ed]
it as a general motion brought under the procedural require-
ments of 10 C.F.R. § 2.730.”5 In rejecting the petition, the
  5
   Since renumbered as 10 C.F.R. § 2.323, this regulation provides, sim-
ply, for “motions”.
               SAN LUIS OBISPO MOTHERS v. NRC              6075
Commission reasoned that by not suspending operating
licenses at installations and power plants following the Sep-
tember 11, 2001 terrorist attacks, it had demonstrated its
implicit conclusion that the continued operation of these facil-
ities neither posed an imminent risk to the public health, nor
was inimical to the common defense. Further, the Commis-
sion concluded that because it had already initiated a thorough
review of its safeguards and physical security program, there
was no reason to suspend the Diablo Canyon licensing pro-
ceeding to address the terrorism-related concerns raised by the
Petitioners. It stated that “[t]here certainly is no reason to
believe that any danger to public health and safety would
result from mere continuation of this adjudicatory proceed-
ing,” given that the proceeding was in its initial stages, that
construction was not scheduled to begin for several years, and
that the Petitioners would be able to comment on any changes
in the rules resulting from the Commission’s ongoing review
of terrorism-related matters if and when they were to occur.

   In a memorandum and order, CLI-03-12, 58 NRC 185
(2003) (“CLI 03-02”), the NRC denied the petitions for
agency review of the Licensing Board’s decisions that “cumu-
latively, rejected challenges to [the PG&E] Installation appli-
cation.” This denial thus became a final order, reviewable by
this court on petition for review. 28 U.S.C. § 2344.

   In October of 2003, the Spent Fuel Project Office of the
NRC’s Office of Material Safety and Safeguards released its
Environmental Assessment Related to the Construction and
Operation of the Diablo Canyon Independent Spent Fuel Stor-
age Installation. The 26-page document contains the NRC’s
conclusion “that the construction, operation, and decommis-
sioning of the Diablo Canyon Installation will not result in
significant impact to the environment,” and therefore that “an
[EIS] is not warranted for the proposed action, and pursuant
to 10 C.F.R. [§] 51.31, a Finding of No Significant Impact is
appropriate.”
6076           SAN LUIS OBISPO MOTHERS v. NRC
   The EA is not devoid of discussion of terrorist attacks.
Indeed, the document contains the Commission’s response to
a comment submitted by the California Energy Commission
in response to an earlier draft that “there is no discussion in
the EA of the potential destruction of the casks or blockage
of air inlet ducts as the result of sabotage or a terrorist attack
. . . [nor is there] a description of how decisions are being
made regarding the configuration, design and spacing of the
casks, the use of berms, and the location of the ISFSI to mini-
mize the vulnerability of the ISFSI to potential attack.” The
NRC responded:

    In several recent cases, . . . the Commission has
    determined that an NRC environmental review is not
    the appropriate forum for the consideration of terror-
    ist acts. The NRC staff considers the security of
    spent fuel as part of its safety review of each applica-
    tion for an ISFSI license. In addition to reviewing an
    ISFSI application against the requirements of 10
    CFR Part 72, the NRC staff evaluates the proposed
    security plans and facility design features to deter-
    mine whether the requirements in 10 CFR Part 73,
    “Physical Protection of Plants and Materials,” are
    met. The details of specific security measures for
    each facility are Safeguards Information, and as
    such, can not be released to the public.

       The NRC has also initiated several actions to fur-
    ther ensure the safety of spent fuel in storage. Addi-
    tional security measures have been put in place at
    nuclear facilities, including ISFSIs currently storing
    spent fuel. These measures include increased secur-
    ity patrols, augmented security forces and weapons,
    additional security posts, heightened coordination
    with law enforcement and military authorities, and
    additional limitations on vehicular access. Also, as
    part of its comprehensive review of its security pro-
    gram, the NRC is conducting several technical
               SAN LUIS OBISPO MOTHERS v. NRC                  6077
    studies to assess potential vulnerabilities of spent
    fuel storage facilities to a spectrum of terrorist acts.
    The results of these studies will be used to determine
    if revisions to the current NRC security requirements
    are warranted.

   Petitioners argue that, in denying their petitions, the NRC
violated the AEA, the APA, and NEPA. Although we reject
the AEA and APA claims, we agree with Petitioners that the
agency has failed to comply with NEPA. We have jurisdiction
over those final orders of the NRC made reviewable by 42
U.S.C. § 2239, which includes final orders entered in licens-
ing proceedings, under 28 U.S.C. § 2342(4).

                              III

   We turn first to Petitioners’ AEA argument. Specifically,
Petitioners argue that the NRC violated its regulations imple-
menting the AEA, as well as the AEA’s hearing provisions,
when it denied Petitioners a hearing on whether NEPA
required consideration of the environmental impact of a ter-
rorist attack on the Storage Installation; they also argue that
the NRC violated the AEA’s hearing provisions in denying
Petitioners a hearing on post-September 11th security mea-
sures for the entire Diablo Canyon complex. Both of these
challenges fail.

                               A

   [1] The NRC did not violate the AEA or its implementing
regulations when it failed to explain its rejection of Petition-
ers’ contentions by addressing each of their arguments. Noth-
ing in the regulations or the AEA requires the NRC to provide
such an explanation.

  Section 189(a) of the AEA grants public hearing rights
“upon the request of any person whose interest may be affect-
ed” by an NRC licensing proceeding. 42 U.S.C. § 2239. The
6078            SAN LUIS OBISPO MOTHERS v. NRC
NRC public hearing regulations, at 10 C.F.R. § 2.309, “pro-
mulgated pursuant to the AEC’s6 power to make, promulgate,
issue, rescind, and amend such rules and regulations as may
be necessary to carry out the purposes of” the AEA, 12 U.S.C.
§ 2201(p), specify the procedures required of both petitioners
and the NRC in making and deciding hearing petitions.

   [2] Petitioners correctly observe that the NRC, in its deci-
sion, did not discuss whether Petitioners satisfied the regula-
tory standard. They are mistaken, however, in their
unsupported contention that this omission amounts to the
agency’s failure to follow its own regulations and thus is “re-
versible error.” The regulations simply do not require the
NRC to explain its decisions in any particular manner.
Although the NRC regulations are specific and demanding in
what they require of petitioners, they demand far less of the
NRC in responding to a petition: the regulations require only
a timely “decision.” See 10 C.F.R. § 2.714(i) (“Decision on
request/petition. The presiding officer shall, within 45 days
after the filing of answers and replies . . . issue a decision on
each request for hearing/petition to intervene.”). Because Peti-
tioners do not claim that the NRC violated this requirement,
we must reject this challenge.

                                 B

   [3] The NRC’s denial of a hearing on whether NEPA
requires consideration of the environmental effects of a terror-
ist attack on the Storage Installation did not violate the AEA’s
hearing provisions.

  [4] Petitioners contend that the NRC relied on an improper
ground in denying their request for a hearing on whether
  6
    In 1974, Congress eliminated the Atomic Energy Commission
(“AEC”). Regulatory functions went to the NRC, and promotional func-
tions to the Energy Research and Development Administration. See
Energy Reorganization Act of 1974, 42 U.S.C. § 5814.
               SAN LUIS OBISPO MOTHERS v. NRC               6079
NEPA requires the Commission to consider the environmen-
tal impacts of terrorism — namely, the ground that it had
determined in earlier decisions that NEPA imposes no such
obligation. Thus, Petitioners do not challenge the substantive
validity or coherence of those earlier opinions in making their
AEA claim, but rather the reliance upon a prior determination
of the merits in order to reject a petition presenting the same
issues. As such, Sierra Club v. NRC, 862 F.2d 222 (9th Cir.
1988), on which Petitioners rely, does not apply. In that case,
the NRC rejected the petitioners’ contentions as lacking in
reasonable specificity, and yet went on to analyze the merits
of those supposedly unacceptable contentions. Id. at 228.
Here, however, where the agency is rejecting the contentions
as contrary to a prior decision, the “merits” and the reason for
the inadmissibility of the contention collapse. Put differently,
the NRC did not reach the merits of the petition as much as
it assessed the issues raised against issues resolved by prior
decisions. We hold that in doing so, the Commission com-
plied fully with the AEA. To hold otherwise would unduly
restrict the agency’s evaluation of hearing petitions, by requir-
ing it to grant a hearing on issues it has already resolved
whenever a petitioner claims to have new evidence. We can
find, and Petitioners point to, nothing in the AEA that would
require this result.

                               C

   [5] The NRC’s denial of a hearing on security measures for
Diablo Canyon as a whole also did not violate the AEA. Peti-
tioners argue that the AEA requires the NRC to grant petition-
ers a hearing on all issues of material fact, including the
security of the entire Diablo Canyon complex. Petitioners
therefore conclude, citing Union of Concerned Scientists v.
NRC, 735 F.2d 1437 (D.C. Cir. 1984), that the NRC violated
the AEA when it denied a hearing on that issue.

   Petitioners’ argument misreads Union of Concerned Scien-
tists, in which the D.C. Circuit held only that the agency can-
6080           SAN LUIS OBISPO MOTHERS v. NRC
not by rule presumptively eliminate a material issue from
consideration in a hearing petition. Union of Concerned Sci-
entists requires the agency to consider a petition; it does not
require that the agency grant it.

   The NRC in CLI 02-23 did not deny that security require-
ments for the entire complex might need to be upgraded, but
rather maintained that a licensing proceeding hearing (and one
regarding an installation, not the entire complex) was not the
correct forum in which to address the issue. The Commission
directed Petitioners to participate in a rulemaking or to raise
their concerns in a hearing then pending before the Licensing
Board. Petitioners contend that these alternative fora are illu-
sory, and that rejection of their petition amounted to the
denial of any opportunity to participate in the consideration of
post-9/11 security measures for the Diablo Canyon complex.

   Petitioners argue “[i]f the NRC were going to resolve Peti-
tioners’ concerns that grossly inadequate security made the
Diablo Canyon facility vulnerable to terrorist attacks generi-
cally, through a rulemaking, such a rulemaking would have
been initiated as a result of the ‘comprehensive security
review’ undertaken by the NRC.” Thus, Petitioners argue that
it would have been futile to submit a rulemaking petition.
This argument must fail, as Petitioners did not use the avail-
able procedures for initiating a rulemaking. Petitioners cannot
complain that NRC failed to institute a rulemaking they never
requested.

   [6] Given that rulemaking may have been an avenue for
Petitioners’ participation, had they chosen to pursue it, their
argument that they had no forum in which to raise their con-
tentions loses its force. However, even were Petitioners cor-
rect in their assertion that they were unfairly denied the
opportunity to participate in a rulemaking proceeding, the
argument that the Licensing Board hearing was similarly illu-
sory would fail. In fact, Petitioners were attempting to use the
present Storage Installation licensing proceeding as a means
               SAN LUIS OBISPO MOTHERS v. NRC             6081
of launching a much broader challenge to the Diablo Canyon
complex. The NRC correctly observes that a petition alleging
that existing NRC regulations are “grossly inadequate to pro-
tect against terrorist attack, and therefore must be supple-
mented by additional requirements” cannot in fact be raised
before the Licensing Board, which cannot hear challenges to
NRC rules. The limited scope of licensing proceedings does
not, however, amount to the arbitrary denial of a forum, as
Petitioners claim. While Petitioners could have raised site-
specific issues “relating to the ‘common defense and securi-
ty’ ” that were not controlled by existing rules or regulations
to the Licensing Board, they are not entitled to expand those
proceedings to include the entire complex, and issues already
covered by agency rules.

                              D

   In short, the NRC did not violate the AEA in denying the
petitions for a hearing. Neither the AEA nor its implementing
regulations required the NRC to grant Petitioners a hearing on
whether NEPA required a consideration of the environmental
impact of a terrorist attack on the Storage Installation or the
security measures adopted for the entire Diablo Canyon com-
plex.

                              IV

   [7] The NRC’s reliance on its own prior opinions in its
decision in this case does not violate the APA’s notice and
comment provisions. Petitioners argue that the decisions in
CLI 03-01 and PFS amount to the announcement “of a gen-
eral policy of refusing to consider the environmental impacts
of terrorist attacks in Environmental Impact Statements.” Peti-
tioners rely on Mada-Luna v. Fitzpatrick, 813 F.2d 1006,
1014 (9th Cir. 1987) to claim that this policy depends on fac-
tual determinations not found subsequent to an evidentiary
proceeding, and constitutes a “binding substantive norm,” the
promulgation of which, without a public hearing, violates the
6082             SAN LUIS OBISPO MOTHERS v. NRC
APA notice and comment provisions contained in 5 U.S.C.
§§ 553(b), (c).7 The flaw in Petitioners’ argument is the mis-
taken assertion that the NRC’s decisions were factual and not
legal. If the NRC’s conclusion that terrorism need not be
examined under NEPA were factual, then Petitioners would
be correct that its determination would have to comply with
APA rulemaking requirements, including notice and com-
ment, or else the agency would have to permit petitioners to
challenge it in every proceeding where it was disputed.

   [8] That NEPA does not require consideration of the envi-
ronmental impacts of terrorism is a legal, and not a factual,
conclusion. Cf. Greenpeace Action v. Franklin, 14 F.3d 1324,
1331 (9th Cir. 1993) (reasoning that a challenge to the ade-
quacy of an EA turned on factual, not legal, principles where
both NEPA’s applicability and the requirements it imposed
were uncontested); see also Alaska Wilderness Recreation &
Tourism Ass’n v. Morrison, 67 F.3d 723, 727 (9th Cir. 1995)
(noting that although “challenges to agency actions which
raise predominantly legal, rather than technical questions, are
rare,” the court was there required to address “just such a
challenge”). Petitioners’ analysis is therefore inapposite. The
agency has the discretion to use adjudication to establish a
binding legal norm. See Sec. & Exch. Comm’n v. Chenery,
332 U.S. 194, 199-203 (1947) (“[T]he choice made between
proceeding by general rule or by individual, ad hoc litigation,
is one that lies primarily in the informed discretion of the
administrative agency.”). We therefore agree with the NRC’s
characterization in its brief to this court: having come to the
legal conclusion that NEPA does not require consideration of
the environmental consequences of terrorist attacks, “[w]hen
  7
    U.S.C. § 553(b) states that “[g]eneral notice of proposed rulemaking
shall be published in the Federal Register,” and outlines the requirements
that such notice must meet. 5 U.S.C. § 553(c) states that after such notice
has been given, “the agency shall give interested persons an opportunity
to participate in the rulemaking through submission of written data, views,
or arguments with or without opportunity for oral presentation.”
               SAN LUIS OBISPO MOTHERS v. NRC               6083
petitioners in this case presented a proposed contention seek-
ing an EIS that analyzed the impacts of possible terrorist acts
at the proposed Diablo Canyon Installation, the NRC reason-
ably concluded that this request was sufficiently similar to the
request in PFS to justify the application of that decision here.”

                               V

   Although we hold that the agency did not violate the APA
when it relied on the prior resolution of a legal issue through
adjudication, we come to a different conclusion as to that
determination’s compliance with NEPA. Because the issue
whether NEPA requires consideration of the environmental
impacts of a terrorist attack is primarily a legal one, we
review the NRC’s determination that it does not for reason-
ableness. See Alaska Wilderness Recreation & Tourism Ass’n,
67 F.3d at 727 (reviewing predominately legal issue for rea-
sonableness because “it makes sense to distinguish the strong
level of deference we accord an agency in deciding factual or
technical matters from that to be accorded in disputes involv-
ing predominately legal questions”); Ka Makani’o Kohala
Ohana, Inc. v. Water Supply, 295 F.3d 955, 959 n.3 (9th Cir.
2002) (“Because this case involved primarily legal issues . . .
based on undisputed historical facts, we conclude that the
‘reasonableness’ standard should apply to this case.”).

   Here, the NRC decided categorically that NEPA does not
require consideration of the environmental effects of potential
terrorist attacks. In making this determination, the NRC relied
on PFS, where it “consider[ed] in some detail the legal ques-
tion whether NEPA requires an inquiry into the threat of ter-
rorism at nuclear facilities.” 56 NRC 340, 343 (2002). In that
case, intervenor State of Utah filed a contention claiming that
the September 11 terrorist attacks “had materially changed the
circumstances under which the Board had rejected previously
proffered terrorism contentions by showing that a terrorist
attack is both more likely and potentially more dangerous
than previously thought.” Id. at 345. The NRC concluded that
6084           SAN LUIS OBISPO MOTHERS v. NRC
even following the September 11th attacks, NEPA did not
impose such a requirement, reasoning:

    In our view, an EIS is not an appropriate format to
    address the challenges of terrorism. The purpose of
    an EIS is to inform the decisionmaking authority and
    the public of a broad range of environmental impacts
    that will result, with a fair degree of likelihood, from
    a proposed project, rather than to speculate about
    ‘worst-case’ scenarios and how to prevent them.

Id. at 347.

   The NRC determined that four grounds “cut[ ] against
using the NEPA framework” to consider the environmental
effects of a terrorist attack: (1) the possibility of a terrorist
attack is far too removed from the natural or expected conse-
quences of agency action; (2) because the risk of a terrorist
attack cannot be determined, the analysis is likely to be mean-
ingless; (3) NEPA does not require a “worst-case” analysis;
and (4) NEPA’s public process is not an appropriate forum for
sensitive security issues. Id. at 348. We review each of these
four grounds for reasonableness, and conclude that these
grounds, either individually or collectively, do not support the
NRC’s categorical refusal to consider the environmental
effects of a terrorist attack.

                               A

   [9] The Commission relied first on finding that the possibil-
ity of a terrorist attack is too far removed from the natural or
expected consequences of agency action. Id. at 347. Section
102 of NEPA requires federal agencies to prepare “a detailed
statement . . . on the environmental impact” of any proposed
major federal action “significantly affecting the quality of the
human environment.” 42 U.S.C. § 4332(1)(C)(i). The ques-
tion thus becomes whether a given action “significantly
affects” the environment.
               SAN LUIS OBISPO MOTHERS v. NRC                6085
   The NRC claims that the appropriate analysis of Section
102 is that employed by the Supreme Court in Metropolitan
Edison Co. v. People Against Nuclear Power, 460 U.S. 766,
773 (1983). In Metropolitan Edison, the Court noted that “[t]o
determine whether Section 102 requires consideration of a
particular effect, we must look to the relationship between
that effect and the change in the physical environment caused
by the major federal action at issue,” looking for “a reason-
ably close causal relationship . . . like the familiar doctrine of
proximate cause from tort law.” 460 U.S. at 774. The Com-
mission claims that its conclusion that the environmental
impacts of a possible terrorist attack on an NRC-licensed
facility is beyond a “reasonably close causal relationship” was
a reasonable application of this “proximate cause” analogy.

   The problem with the agency’s argument, however, is that
Metropolitan Edison and its proximate cause analogy are
inapplicable here. In Metropolitan Edison, the petitioners
argued that NEPA required the NRC to consider the potential
risk of psychological damage upon reopening the Three Mile
Island nuclear facilities to those in the vicinity. Noting that
NEPA is an environmental statute, the Supreme Court held
that the essential analysis must focus on the “closeness of the
relationship between the change in the environment and the
‘effect’ at issue.” 460 U.S. at 772.

   The appropriate analysis is instead that developed by this
court in NoGwen Alliance v. Aldridge, 855 F.2d 1380 (9th
Cir. 1988). In NoGwen, the plaintiffs argued that NEPA
required the Air Force to consider the threat of nuclear war in
the implementation of the Ground Wave Emergency Network
(“GWEN”). We held “that the nexus between construction of
GWEN and nuclear war is too attenuated to require discussion
of the environmental impacts of nuclear war in an [EA] or
[EIS].” 855 F.2d at 1386.

  [10] The events at issue here, as well as in Metropolitan
Edison and NoGwen, form a chain of three events: (1) a major
6086           SAN LUIS OBISPO MOTHERS v. NRC
federal action; (2) a change in the physical environment; and
(3) an effect. Metropolitan Edison was concerned with the
relationship between events 2 and 3 (the change in the physi-
cal environment, or increased risk of accident resulting from
the renewed operation of a nuclear reactor, and the effect, or
the decline in the psychological health of the human popula-
tion). The Court in Metropolitan Edison explicitly distin-
guished the case where the disputed relationship is between
events 1 and 2: “we emphasize that in this case we are consid-
ering effects caused by the risk of accident. The situation
where an agency is asked to consider effects that will occur
if a risk is realized, for example, if an accident occurs . . . is
an entirely different case.” Id. at 775 n.9. In NoGwen, we fol-
lowed the Court’s admonition and, in addressing the relation-
ship between events 1 and 2, we held that the Metropolitan
Edison analysis did not apply “because it discusse[d] a differ-
ent type of causation than that at issue in this case . . . [which]
require[d] us to examine the relationship between the agency
action and a potential impact on the environment.” Id. at
1386. NoGWEN relied on our decision in Warm Springs Dam
Task Force v. Gribble, 621 F.2d 1017, 1026 (9th Cir. 1980),
which held that “an impact statement need not discuss remote
and highly speculative consequences.” Applying that standard
to the plaintiffs’ claims that the military GWEN system’s
installation would “increase the probability of nuclear war,”
and “that GWEN would be a primary target in a nuclear war,”
we held both propositions to be “remote and highly specula-
tive,” and, therefore, NEPA did not require their consider-
ation.

   [11] In the present case, as in NoGwen, the disputed rela-
tionship is between events 1 and 2 (the federal act, or the
licensing of the Storage Installation, and the change in the
physical environment, or the terrorist attack). The appropriate
inquiry is therefore whether such attacks are so “remote and
highly speculative” that NEPA’s mandate does not include
consideration of their potential environmental effects.
               SAN LUIS OBISPO MOTHERS v. NRC                6087
   [12] The NRC responds by simply declaring without sup-
port that, as a matter of law, “the possibility of a terrorist
attack . . . is speculative and simply too far removed from the
natural or expected consequences of agency action to require
a study under NEPA.” 56 NRC at 349. In doing so, the NRC
failed to address Petitioners’ factual contentions that licensing
the Storage Installation would lead to or increase the risk of
a terrorist attack because (1) the presence of the Storage
Installation would increase the probability of a terrorist attack
on the Diablo Canyon nuclear facility, and (2) the Storage
Installation itself would be a primary target for a terrorist
attack. We conclude that it was unreasonable for the NRC to
categorically dismiss the possibility of terrorist attack on the
Storage Installation and on the entire Diablo Canyon facility
as too “remote and highly speculative” to warrant consider-
ation under NEPA.

   [13] In so concluding, we also recognize that the NRC’s
position that terrorist attacks are “remote and highly specula-
tive,” as a matter of law, is inconsistent with the government’s
efforts and expenditures to combat this type of terrorist attack
against nuclear facilities. In the PFS opinion, the NRC
emphasized the agency’s own post-September 11th efforts
against the threat of terrorism:

    At the outset, however, we stress our determination,
    in the wake of the horrific September 11th terrorist
    attacks, to strengthen security at facilities we regu-
    late. We currently are engaged in a comprehensive
    review of our security regulations and programs, act-
    ing under our AEA-rooted duty to protect “public
    health and safety” and the “common defense and
    security.” We are reexamining, and in may cases
    have already improved, security and safeguards mat-
    ters such as guard force size, physical security exer-
    cises, clearance requirements and background
    investigations for key employees, and fitness-for-
    duty requirements. More broadly, we are rethinking
6088              SAN LUIS OBISPO MOTHERS v. NRC
      the NRC’s threat assessment framework and design
      basis threat. We also are reviewing our own infra-
      structure, resources, and communications.

         Our comprehensive review may also yield perma-
      nent rule or policy changes that will apply to the pro-
      posed PFS facility and to other NRC-related
      facilities. The review process is ongoing and cumu-
      lative. It has already resulted in a number of
      security-related actions to address terrorism threats
      at both active and defunct nuclear facilities.

56 NRC at 343. Among these actions is the establishment of
an Office of Nuclear Security and Incident Response, “re-
sponsible for immediate operational security and safeguards
issues as well as for long-term policy development[,] work[-
ing] closely with law enforcement agencies and the Office of
Homeland Security[,] . . . coordinat[ing] the NRC’s ongoing
comprehensive security review.” Id. at 344-45.

   We find it difficult to reconcile the Commission’s conclu-
sion that, as a matter of law, the possibility of a terrorist attack
on a nuclear facility is “remote and speculative,” with its
stated efforts to undertake a “top to bottom” security review
against this same threat. Under the NRC’s own formulation of
the rule of reasonableness, it is required to make determina-
tions that are consistent with its policy statements and proce-
dures. Here, it appears as though the NRC is attempting, as a
matter of policy, to insist on its preparedness and the serious-
ness with which it is responding to the post-September 11th
terrorist threat, while concluding, as a matter of law, that all
terrorist threats are “remote and highly speculative” for NEPA
purposes.8
  8
   The view that a terrorist attack is too speculative to be a required part
of NEPA review would seem to be inconsistent with the NRC’s pre-9/11
security procedures. Since 1977, the NRC has required licensed plants to
have a security plan that is designed to protect against a “design basis
                 SAN LUIS OBISPO MOTHERS v. NRC                      6089
   [14] In sum, in considering the policy goals of NEPA and
the rule of reasonableness that governs its application, the
possibility of terrorist attack is not so “remote and highly
speculative” as to be beyond NEPA’s requirements.

                                    B

   [15] The NRC’s reliance upon the second PFS factor, that
the Risk of a Terrorist Attack Cannot be Adequately Deter-
mined, 56 NRC at 350, is also not reasonable. First, the
NRC’s dismissal of the risk of terrorist attacks as “unquantifi-
able” misses the point. The numeric probability of a specific
attack is not required in order to assess likely modes of attack,
weapons, and vulnerabilities of a facility, and the possible
impact of each of these on the physical environment, includ-
ing the assessment of various release scenarios. Indeed, this
is precisely what the NRC already analyzes in different con-
texts. It is therefore possible to conduct a low probability-high
consequence analysis without quantifying the precise proba-
bility of risk. The NRC itself has recognized that consider-
ation of uncertain risks may take a form other than
quantitative “probabilistic” assessment. In its “Proposed Pol-
icy Statement on Severe Accidents and Related Views on
Nuclear Reactor Regulation,” 48 Fed.Reg. 16,014 (1983), the
Commission stated that:

threat” for radiological sabotage. See General Accounting Office, Nuclear
Regulatory Commission: Oversight of Security at Commercial Nuclear
Power Plants Needs to be Strengthened, GAO-030752 (2003) at 6. “The
design basis threat characterizes the elements of a postulated attack,
including the number of attackers, their training, and the weapons and tac-
tics they are capable of using.” Id.
   Thus, the NRC—even before the terrorist attacks of 9/11—did not con-
sider such attacks too “remote and speculative” to be considered in agency
planning. To the contrary, the agency has long required analysis of means
and methods of hypothetical attacks against specific facilities, with the
goal of establishing effective counter-measures.
6090           SAN LUIS OBISPO MOTHERS v. NRC
    In addressing potential accident initiators (including
    earthquakes, sabotage, and multiple human errors)
    where empirical data are limited and residual uncer-
    tainty is large, the use of conceptual modeling and
    scenario assumptions in Safety Analysis Reports will
    be helpful. They should be based on the best quali-
    fied judgments of experts, either in the form of sub-
    jective numerical probability estimates or qualitative
    assessments of initiating events and casual [sic]
    linkages in accident sequences.

48 Fed.Reg. at 16,020 (emphasis added).

   [16] No provision of NEPA, or any other authority cited by
the Commission, allows the NRC to eliminate a possible envi-
ronmental consequence from analysis by labeling the risk as
“unquantifiable.” See Limerick Ecology Action, Inc. v. NRC,
869 F.2d 719, 754 (3rd Cir. 1989) (J. Scirica, dissenting)
(finding no “statutory provision, no NRC regulation or policy
statement, and no case law that permits the NRC to ignore any
risk found to be unquantifiable”). If the risk of a terrorist
attack is not insignificant, then NEPA obligates the NRC to
take a “hard look” at the environmental consequences of that
risk. The NRC’s actions in other contexts reveal that the
agency does not view the risk of terrorist attacks to be insig-
nificant. Precise quantification is therefore beside the point.

   Even if we accept the agency’s argument, the agency fails
to adequately show that the risk of a terrorist act is unquantifi-
able. The agency merely offers the following analysis as to
the quantifiability of a potential terrorist attack:

    The horrors of September 11 notwithstanding, it
    remains true that the likelihood of a terrorist attack
    being directed at a particular nuclear facility is not
    quantifiable. Any attempt at quantification or even
    qualitative assessment would be highly speculative.
    In fact, the likelihood of attack cannot be ascertained
                  SAN LUIS OBISPO MOTHERS v. NRC                        6091
      with confidence by any state-of-the-art methodology.
      That being the case, we have no means to assess,
      usefully, the risks of terrorism at the PFS facility.

56 NRC at 350. The agency nonetheless has simultaneously
shown the ability to conduct a “top to bottom” terrorism
review. This leaves the Commission in the tenuous position
of insisting on the impossibility of a meaningful, i.e. quantifi-
able, assessment of terrorist attacks, while claiming to have
undertaken precisely such an assessment in other contexts.
Further, as we have noted, the NRC has required site-specific
analysis of such threats, involving numerous recognized scenar-
ios.9

   [17] Thus, we conclude that precise quantification of a risk
is not necessary to trigger NEPA’s requirements, and even if
it were, the NRC has not established that the risk of a terrorist
attack is unquantifiable.

                                     C

   The NRC’s third ground, that it is not required to conduct
a “worst-case” analysis, is a non sequitur. Although it is a true
statement of the law, the agency errs in equating an assess-
ment of the environmental impact of terrorist attack with a
demand for a worst-case analysis.

   The Council on Environmental Quality (“CEQ”) regula-
tions, 40 C.F.R. §§ 1500.1 - 1518.4, promulgated with the
“purpose [of] tell[ing] federal agencies what they must do to
comply with [NEPA] procedures and achieve the goals of
  9
    The NRC’s assertion that a risk of terrorism cannot be quantified is
also belied by the very existence of the Department of Homeland Security
Advisory System, which provides a general assessment of the risk of ter-
rorist attacks. See, e.g., World Market Research Centre, Global Terrorism
Index 2003/4 (offering a probabilistic risk assessment of terrorist activities
over a 12-month period).
6092           SAN LUIS OBISPO MOTHERS v. NRC
[NEPA],” have been interpreted by the Supreme Court as “en-
titled to substantial deference.” Robertson v. Methow Valley
Citizens Council, 490 U.S. 332, 355 (citing Andrus v. Sierra
Club, 442 U.S. 347, 358 (1979)). These regulations mandated
worst-case analyses until 1986, when CEQ replaced the for-
mer 40 C.F.R. § 1502.22, requiring an agency, when relevant
information was either unavailable or too costly to obtain, to
include in the EIS a “worst-case analysis and an indication of
the probability or improbability of its occurrence,” with the
new and current version of the regulation, which requires an
agency to instead deal with uncertainties by including within
the EIS “a summary of existing credible scientific evidence
which is relevant to evaluating the reasonable foreseeable sig-
nificant adverse impacts on the human environment, and . . .
the agency’s evaluation of such impacts based upon theoreti-
cal approaches or research methods generally accepted in the
scientific community.” 40 C.F.R. §§ 1502.22(b)(3), (4). The
current requirement applies to those events with potentially
catastrophic consequences “even if their probability of occur-
rence is low, provided that the analysis of impacts is sup-
ported by credible scientific evidence, is not based on pure
conjecture, and is within the rule of reason.” 40 C.F.R.
§ 1502.22 (b)(4). The Supreme Court held in Robertson that
the amendment of the regulations had nullified the worst-case
analysis requirement. 490 U.S. at 355; Edwardsen v. U.S.
Dep’t of Interior, 268 F.3d 781, 785 (9th Cir. 2001).

   The Commission is therefore correct when it argues that
NEPA does not require a worst-case analysis. It is mistaken,
however, when it claims that “Petitioners’ request for an anal-
ysis of [the environmental effects of] a successful terrorist
attack at the Diablo Canyon ISFSI approximates a request for
a ‘worst-case’ analysis that has long since been discarded by
the CEQ regulations . . . and discredited by the Federal
courts.” According to the NRC, “[m]aking the various
assumptions required by [P]etitioners’ scenario requires the
NRC to venture into the realm of ‘pure conjecture.’ ” We dis-
agree.
                  SAN LUIS OBISPO MOTHERS v. NRC                      6093
   [18] An indication of what CEQ envisioned when it
imposed the worst-case analysis requirement can be gleaned
from a 1981 CEQ memorandum, Forty Most Asked Questions
Concerning CEQ’s National Environmental Policy Act Regu-
lations, reprinted at 46 FR 18026-01 (March 23, 1981). CEQ
answered one of those questions, “[w]hat is the purpose of a
worst-case analysis? How is it formulated and what is the
scope of the analysis?” with the following:

       The purpose of the analysis is to . . . cause agencies
       to consider th[ ]e potential consequences [of agency
       decisions] when acting on the basis of scientific
       uncertainties or gaps in available information. The
       analysis is formulated on the basis of available infor-
       mation, using reasonable projections of the worst
       possible consequences of a proposed action.

          For example, if there are scientific uncertainty and
       gaps in the available information concerning the
       numbers of juvenile fish that would be entrained in
       a cooling water facility, the responsible agency must
       disclose and consider the possibility of the loss of
       the commercial or sport fishery. In addition to an
       analysis of a low probability/catastrophic impact
       event, the worst-case analysis should also include a
       spectrum of events of higher probability but less
       drastic impact.

46 FR 18026, 18032. While it is true that the agency is not
required to consider consequences that are “speculative,”10 the
  10
     Because we disagree with the agency’s interpretation of worst-case
analysis, we do not reach the agency’s characterization of the possibility
of terrorist attack as “speculative.” We note, however, that this character-
ization stands out as contrary to the vigilant stance that Americans are
encouraged to take by the Department of Homeland Security. See
www.dhs.gov/dhspublic/display?theme=29 (urging that “[a]ll Americans
should continue to be vigilant” and noting that “[t]he country remains at
an elevated risk . . . for terrorist attack.”)
6094           SAN LUIS OBISPO MOTHERS v. NRC
NRC’s argument wrongly labels a terrorist attack the worst-
case scenario because of the low or indeterminate probability
of such an attack. The CEQ memo, by including as worst-case
scenarios events of both higher and lower probability, reveals
that worst-case analysis is not defined solely by the low prob-
ability of the occurrence of the events analyzed, but also by
the range of outcomes of those events. See also Greater Yel-
lowstone Coalition v. Flowers, 321 F.3d 1250, 1260 (10th
Cir. 2003) (citing a witness’s testimony that the loss of bald
eagle nesting sites was both “likely” and “a worst-case sce-
nario”). Petitioners do not seek to require the NRC to analyze
the most extreme (i.e., the “worst”) possible environmental
impacts of a terrorist attack. Instead, they seek an analysis of
the range of environmental impacts likely to result in the
event of a terrorist attack on the Storage Installation. We
reject the Commission’s characterization of this request as a
demand for a worst-case analysis.

                               D

   [19] The NRC’s reliance on the fourth PFS factor, that it
cannot comply with its NEPA mandate because of security
risks, is also unreasonable. There is no support for the use of
security concerns as an excuse from NEPA’s requirements.
While it is true, as the agency claims, that NEPA’s require-
ments are not absolute, and are to be implemented consistent
with other programs and requirements, this has never been
interpreted by the Supreme Court as excusing NEPA’s appli-
cation to a particularly sensitive issue. See Weinberger v.
Catholic Action of Hawaii, 454 U.S. 139 (1981) (holding that
the Navy was required to perform a NEPA review and to fac-
tor its results into decisionmaking even where the sensitivity
of the information involved meant that the NEPA results
could not be publicized or adjudicated). Weinberger can sup-
port only the proposition that security considerations may per-
mit or require modification of some of the NEPA procedures,
not the Commission’s argument that sensitive security issues
result in some kind of NEPA waiver.
               SAN LUIS OBISPO MOTHERS v. NRC              6095
   The application of NEPA’s requirements, under the rule of
reason relied on by the NRC, is to be considered in light of
the two purposes of the statute: first, ensuring that the agency
will have and will consider detailed information concerning
significant environmental impacts; and, second, ensuring that
the public can both contribute to that body of information, and
can access the information that is made public. Pub. Citizen,
541 U.S. at 768. To the extent that, as the NRC argues, certain
information cannot be publicized, as in Weinberger, other
statutory purposes continue to mandate NEPA’s application.
For example, that the public cannot access the resulting infor-
mation does not explain the NRC’s determination to prevent
the public from contributing information to the decisionmak-
ing process. The NRC simply does not explain its unwilling-
ness to hear and consider the information that Petitioners seek
to contribute to the process, which would fulfill both the
information-gathering and the public participation functions
of NEPA. These arguments explain why a Weinberger-style
limited proceeding might be appropriate, but cannot support
the NRC’s conclusion that NEPA does not apply. As we
stated in NoGWEN : “There is no ‘national defense’ exception
to NEPA . . . ‘The Navy, just like any federal agency, must
carry out its NEPA mandate to the fullest extent possible and
this mandate includes weighing the environmental costs of the
[project] even though the project has serious security implica-
tions.’ ” 855 F.2d at 1384 (quoting Concerned About Trident
v. Rumsfeld, 555 F.2d 817, 823 (D.C. Cir. 1977)).

                               E

   [20] In sum, none of the four factors upon which the NRC
relies to eschew consideration of the environmental effects of
a terrorist attack satisfies the standard of reasonableness. We
must therefore grant the petition in part and remand for the
agency to fulfill its responsibilities under NEPA.

 [21] Our identification of the inadequacies in the agency’s
NEPA analysis should not be construed as constraining the
6096           SAN LUIS OBISPO MOTHERS v. NRC
NRC’s consideration of the merits on remand, or circumscrib-
ing the procedures that the NRC must employ in conducting
its analysis. There remain open to the agency a wide variety
of actions it may take on remand, consistent with its statutory
and regulatory requirements. We do not prejudge those alter-
natives. Nor do we prejudge the merits of the inquiry. We
hold only that the NRC’s stated reasons for categorically
refusing to consider the possibility of terrorist attacks cannot
withstand appellate review based on the record before us.

   We are also mindful that the issues raised by the petition
may involve questions of national security, requiring sensitive
treatment on remand. However, the NRC has dealt with our
nation’s most sensitive nuclear secrets for many decades, and
is well-suited to analyze the questions raised by the petition
in an appropriate manner consistent with national security.

                              VI

   We deny the petition as to the claims under the AEA and
the APA. However, because we conclude that the NRC’s
determination that NEPA does not require a consideration of
the environmental impact of terrorist attacks does not satisfy
reasonableness review, we hold that the EA prepared in reli-
ance on that determination is inadequate and fails to comply
with NEPA’s mandate. We grant the petition as to that issue
and remand for further proceedings consistent with this opin-
ion.

 PETITION GRANTED IN PART; DENIED IN PART;
REMANDED.
