 United States Court of Appeals
         FOR THE DISTRICT OF COLUMBIA CIRCUIT



Argued March 20, 2018                  Decided August 7, 2018

                         No. 17-5067

              MOATH HAMZA AHMED AL-ALWI,
                      APPELLANT

                              v.

            DONALD J. TRUMP, PRESIDENT, ET AL.,
                        APPELLEES


        Appeal from the United States District Court
                for the District of Columbia
                    (No. 1:15-cv-00681)


   Ramzi Kassem argued the cause for the appellant. John J.
Connolly and Beth D. Jacob were with him on the briefs.

    Jennifer R. Cowan was on brief for the amicus curiae
Experts on International Law and Foreign Relations Law in
support of initial hearing En Banc.

     Sonia M. Carson, Attorney, United States Department of
Justice, argued the cause for the appellees. Douglas N. Letter,
Matthew M. Collette and Sonia K. McNeil, Attorneys, were on
brief. Sharon Swingle, Attorney, entered an appearance.

    Before: GARLAND, Chief Judge, and HENDERSON and
GRIFFITH, Circuit Judges.
                                2
    Opinion for the Court filed by Circuit Judge HENDERSON.

     KAREN LECRAFT HENDERSON, Circuit Judge: Moath
Hamza Ahmed Al-Alwi, a detainee at the United States Naval
Base at Guantanamo Bay, Cuba, petitioned for a writ of habeas
corpus. The district court denied the petition. On appeal, Al-
Alwi argues that the conflict resulting in his detention is so
unprecedented that the United States’ authority to detain him
has unraveled. He also argues in the alternative that the conflict
has ended, thereby terminating the United States’ authority to
detain him. Finally, he advances due process claims and a
request for further fact-finding. For the following reasons, we
affirm the judgment of the district court denying Al-Alwi’s
petition.

                        I. Background

    Shortly after the terrorist attacks of September 11, 2001,
the Congress authorized the President to

       use all necessary and appropriate force against
       those nations, organizations, or persons he
       determines planned, authorized, committed, or
       aided the terrorist attacks that occurred on
       September 11, 2001, or harbored such
       organizations or persons, in order to prevent any
       future acts of international terrorism against the
       United States by such nations, organizations or
       persons.

     Authorization for Use of Military Force, Pub. L. No. 107-
40, § 2(a), 115 Stat. 224, 224 (Sept. 18, 2001) (AUMF).

    Ten years later, the Congress “affirm[ed] that the authority
of the President to use all necessary and appropriate force
pursuant to” the AUMF “includes the authority” to “detain”
                               3
persons who “w[ere] a part of or substantially supported al-
Qaeda, the Taliban, or associated forces that are engaged in
hostilities against the United States.” National Defense
Authorization Act for Fiscal Year 2012, Pub. L. No. 112-81,
§ 1021(a), (b)(2), 125 Stat. 1298, 1562 (Dec. 31, 2011). The
Congress granted authority to detain such persons “under the
law of war without trial until the end of the hostilities
authorized by the” AUMF. Id. § 1021(c)(1).

     Al-Alwi is a Yemeni citizen who grew up in Saudi Arabia.
According to the Government and uncontested in this appeal,
Al-Alwi stayed in Taliban guesthouses, traveled to a Taliban-
linked training camp to learn how to fire rifles and grenade
launchers and joined a combat unit led by an al Qaeda official
that fought alongside the Taliban. Al Alwi v. Obama (Al Alwi
I), 653 F.3d 11, 13–14 (D.C. Cir. 2011); see id. at 20 (noting
that Al-Alwi “did not deny” that “majority of the principal
facts” Government asserted “were true” (internal quotation
omitted)). Al-Alwi was captured in December 2001 and turned
over to United States authorities, who detained him at
Guantanamo Bay pursuant to the AUMF. Al-Alwi remains at
Guantanamo Bay today.

    In 2005, Al-Alwi petitioned for a writ of habeas corpus.
The district court denied the petition after concluding that the
Government’s account of Al-Alwi’s Taliban-related activities
was supported by a preponderance of the evidence, thereby
making Al-Alwi an enemy combatant who could lawfully be
detained. Al Alwi v. Bush, 593 F. Supp. 2d 24, 27–29 (D.D.C.
2008). This Court affirmed. Al Alwi I, 653 F.3d at 15–20.

    In 2009, the President established an intra-branch process
to “review . . . the factual and legal bases for the continued
detention of all individuals” held at Guantanamo Bay. Review
and Disposition of Individuals Detained At the Guantanamo
                                4
Bay Naval Base and Closure of Detention Facilities, Exec.
Order No. 13,492 § 2(d), 74 Fed. Reg. 4,897, 4,898 (Jan. 22,
2009). As part of the ongoing process, a Periodic Review Board
comprised of senior Executive Branch officials must
“periodic[ally] review” detentions at Guantanamo Bay to
“ensure” that continued military detentions are “justified.”
Periodic Review of Individuals Detained at Guantanamo Bay
Naval Station Pursuant to the Authorization for Use of Military
Force, Exec. Order No. 13,567, 76 Fed. Reg. 13,277 (Mar. 7,
2011). In October 2015, the Periodic Review Board determined
that continued detention of Al-Alwi “remain[ed] necessary to
protect against a continuing significant threat to the security of
the United States.” Joint Appendix (JA) 641.

    In 2015, Al-Alwi filed a second petition for a writ of
habeas corpus, which is the subject of this appeal. Al-Alwi did
not challenge the district court’s earlier determination that he
remains an enemy combatant. Instead, Al-Alwi alleged that the
conflict in Afghanistan that resulted in his detention had ended
and therefore the United States “no longer [had] any lawful
basis” to detain him. JA 11.

    The district court denied the petition. Al-Alwi v. Trump,
236 F. Supp. 3d 417 (D.D.C. 2017). This appeal followed.

                         II. Analysis

     On appeal from denial of a habeas petition, we review the
“district court’s findings of fact for clear error, its habeas
determination de novo, and any challenged evidentiary rulings
for abuse of discretion.” Barhoumi v. Obama, 609 F.3d 416,
423 (D.C. Cir. 2010). As stated earlier, the Government’s
initial authority to detain Al-Alwi as an enemy combatant after
his capture has been asked and answered in the affirmative, Al
Alwi I, 653 F.3d 11, and remains unaffected by this petition and
appeal. Instead, Al-Alwi’s petition advances two arguments to
                               5
support his claim that the Government’s established detention
authority has expired. First, Al-Alwi argues that the United
States’ authority to detain him has “unraveled” because the
conflict in which he participated is a new species of conflict
uninformed by the previous law of war. Second, and
alternatively, Al-Alwi argues that the conflict has ended. On a
separate and final note, Al-Alwi asserts on appeal due process
violations and a need for further discovery in district court. We
reject all of Al-Alwi’s arguments.

         A. Authority to detain has not unraveled

     The Congress’s “grant of authority” in the AUMF “for the
use of ‘necessary and appropriate force,’” the United States
Supreme Court has held, authorizes detention of enemy
combatants “for the duration of the particular conflict in which
they were captured.” Hamdi v. Rumsfeld, 542 U.S. 507, 518,
521 (2004) (plurality opinion) (quoting AUMF); accord id. at
579 (Thomas, J., dissenting) (“The Executive Branch . . . has
determined that [petitioner] is an enemy combatant and should
be detained. This detention falls squarely within the Federal
Government’s war powers, and we lack the expertise and
capacity to second-guess that decision. As such, petitioners’
habeas challenge should fail . . . .”); see Uthman v. Obama, 637
F.3d 400, 402 (D.C. Cir. 2011) (“The AUMF . . . authorizes the
Executive Branch to detain” enemy combatants “for the
duration of hostilities.”). And the 2012 National Defense
Authorization Act permits “[d]etention under the law of
war . . . until the end of the hostilities authorized by the”
AUMF. Pub. L. No. 112-81, § 1021(c)(1). Neither of these
enactments places limits on the length of detention in an
ongoing conflict. Our baseline, then, is that the AUMF remains
in force if hostilities between the United States and the Taliban
and al Qaeda continue. See Ali v. Obama, 736 F.3d 542, 552
(D.C. Cir. 2013) (“[T]he 2001 AUMF does not have a time
                                6
limit, and the Constitution allows detention of enemy
combatants for the duration of hostilities.”). Such hostilities
continue, as discussed in more detail infra. See, e.g., Redacted
Declaration of Rear Admiral Andrew L. Lewis ¶¶ 11–12 (Feb.
1, 2016), JA 754–55 (“Fighting [between the Taliban and U.S.
forces] has been nearly continuous since February 2015
. . . . From January 2015 to [February 2016], there have been
numerous, specific instances of hostile forces, including the
Taliban and al-Qaeda, attacking or planning to attack U.S.
personnel and facilities in Afghanistan.”); United States Air
Forces Central Command, 2010–2015 Airpower Statistics
(Oct. 31, 2015), JA 579 (indicating United States released 847
weapons during 2015).

     Nevertheless, Al-Alwi maintains that traditional law-of-
war principles, which the Hamdi plurality said grounded its
“understanding” of the AUMF’s detention authority, 542 U.S.
at 521, do not apply to the conflict here because of the conflict’s
duration, geographic scope and variety of parties involved. The
“unprecedented” circumstances of the Afghanistan-based
conflict, Al-Alwi argues, “ha[ve] eroded the United States’
detention authority under the AUMF.” Appellant’s Br. 17. But
Al-Alwi’s cited authorities, see Appellant’s Br. 16, merely
suggest the possibility that the duration of a conflict may affect
the Government’s detention authority and, in any event, are not
controlling. See Hamdi, 542 U.S. at 521 (plurality opinion)
(“understanding” of detention authority “may unravel” if
circumstances of conflict “are entirely unlike those” of
previous conflicts (emphasis added)); Boumediene v. Bush, 553
U.S. 723, 771 (2008) (holding that Constitution applies at
Guantanamo Bay and noting, in context of rejecting
Government argument that such holding would be
unprecedented, conflict resulting in Guantanamo Bay detention
“is already among the longest wars in American history”);
Hussain v. Obama, 134 S. Ct. 1621, 1622 (2014) (statement of
                                 7
Breyer, J., respecting denial of certiorari) (Court has not
“considered whether, assuming detention . . . is permissible,
either the AUMF or the Constitution limits the duration of
detention”). These statements, then, do not provide a
“foundation” for Al-Alwi’s theory to prevail or persuade. Al-
Bihani v. Obama, 590 F.3d 866, 875 (D.C. Cir. 2010) (rejecting
petitioner’s “clean hands” theory he argued undermined
Government’s authority to detain him in part because “the
citation [petitioner] gives to support his theory is not
controlling”).

     Moreover, Al-Alwi has not identified any international
law principle affirmatively stating that detention of enemy
combatants may not continue until the end of active hostilities,
even in a long war. Instead, law-of-war principles are open-
ended and unqualified on the subject. See Hamdi, 542 U.S. at
520 (plurality opinion) (citing Article 118 of the Geneva
Convention (III) Relative to the Treatment of Prisoners of War
and Article 20 of the Hague Convention (II) on Laws and
Customs of War on Land as support for “clearly established
principle of the law of war” that detention may continue during
“active hostilities”); accord id. at 588 (Thomas, J., dissenting)
(noting that “the power to detain does not end with the
cessation of formal hostilities”). Nor has Al-Alwi advanced an
alternative detention rule that should apply at this point.
Although he urges that we “must impose a limit” on the
Government’s statutory authority to continue detaining him,
Appellant’s Br. 21, he provides no description of a limit and
points to no controlling authority setting a possible limit. Cf.
Ali, 736 F.3d at 552 (“[A]bsent a statute that imposes a time
limit or creates a sliding-scale standard that becomes more
stringent over time, it is not the Judiciary’s proper role to devise
a novel detention standard that varies with the length of
detention.”).
                               8
     Accordingly, we continue to follow Hamdi’s
interpretation of the AUMF and the National Defense
Authorization Act’s plain language. Both of those sources
authorize detention until the end of hostilities. Although
hostilities have been ongoing for a considerable amount of
time, they have not ended. As in Hamdi, then, “the situation we
face” does not support Al-Alwi’s theory of unraveling
authority because “[a]ctive combat operations against Taliban
fighters apparently are ongoing in Afghanistan.” 542 U.S. at
521 (plurality opinion). Therefore, we reject Al-Alwi’s
argument that the United States’ authority to detain him has
“unraveled.”

          B. Authority to detain has not expired

    In the alternative, Al-Alwi argues that the United States’
detention authority has expired because the “relevant conflict,”
Hamdi, 542 U.S. at 521 (plurality opinion), in which he was
captured and detained has ended. We disagree.

     The “termination” of hostilities is “a political act.”
Ludecke v. Watkins, 335 U.S. 160, 168–69 (1948). If the “life
of a statute” conferring war powers on the Executive “is
defined by the existence of a war, Congress leaves the
determination of when a war is concluded to the usual political
agencies of the Government.” Id. at 169 n.13; see also Al-
Bihani, 590 F.3d at 874 (in absence of Congressional definition
of end of war, “we defer to the Executive’s opinion on the
matter”). “Whether and when it would be open to this Court to
find that a war though merely formally kept alive had in fact
ended, is a question too fraught with gravity even to be
adequately formulated when not compelled.” Ludecke, 335
U.S. at 169.

    The question alluded to in Ludecke is not compelled here.
The AUMF authorizes detention for the duration of the conflict
                               9
between the United States and the Taliban and al Qaeda.
National Defense Authorization Act, Pub. L. No. 112-81,
§ 1021(a), (b)(2), (c)(1); Uthman, 637 F.3d at 402. We
affirmed the district court’s earlier determination that Al-Alwi
was part of either the Taliban or al Qaeda. Al Alwi I, 653 F.3d
at 15–20. The Executive Branch represents that armed
hostilities between United States forces and those entities
persist. See Letter from the President to the Speaker of the
House of Representatives and the President Pro Tempore of the
Senate (June 13, 2016) (“The United States currently remains
in an armed conflict against al-Qa’ida, the Taliban, and
associated forces, and active hostilities against those groups
remain ongoing.”), JA 885; Letter from the President to the
Speaker of the House of Representatives and the President Pro
Tempore of the Senate (June 6, 2017) (“The United States
remains in an armed conflict [in Afghanistan], including
against the Taliban, and active hostilities remain ongoing.”),
perma.cc/Q769-DKQY. The record confirms the Executive
Branch’s representations. See, e.g., Redacted Declaration of
Rear Admiral Andrew L. Lewis ¶¶ 11–12 (Feb. 1, 2016), JA
754–55 (“Fighting [between the Taliban and U.S. forces] has
been nearly continuous since February 2015. . . . From January
2015 to [February 2016], there have been numerous, specific
instances of hostile forces, including the Taliban and al-Qaeda,
attacking or planning to attack U.S. personnel and facilities in
Afghanistan.”); United States Air Forces Central Command,
2010–2015 Airpower Statistics (Oct. 31, 2015), JA 579
(indicating United States released 847 weapons during 2015);
Statement of Gen. John F. Campbell (Mar. 4, 2015), JA 124
(“[W]e continue to attack the remnants of al-Qaeda” in
Afghanistan). Al-Alwi does not contest the accuracy of this
record and his counsel conceded at oral argument that “there is
a shooting war in Afghanistan [that] involves U.S. elements.”
Oral Arg. Tr. 39:19–20.
                               10
     Al-Alwi argues that the nature of the hostilities has
changed such that the “particular conflict in which [he was]
captured,” Hamdi, 542 U.S. at 518 (plurality opinion), is not
the same conflict that remains ongoing today. Al-Alwi was
captured during Operation Enduring Freedom, the U.S.
military campaign launched in 2001 to “defeat[] al Qaeda” and
remove the Taliban from power in Afghanistan. JA 64.
President Obama announced the “end” of Operation Enduring
Freedom at the end of 2014. JA 63. President Obama
contemporaneously announced the “begin[ning]” of Operation
Freedom’s Sentinel. JA 63. The new Operation “pursue[d] two
missions”: to “continue [supporting] Afghan security forces”
and to “continue our counterterrorism mission against the
remnants of Al-Qaeda.” JA 63. The transition from Operation
Enduring Freedom to Operation Freedom’s Sentinel, Al-Alwi
contends, terminated the Government’s power under the
AUMF to detain him.

      We disagree. As indicated above, the AUMF authorizes
detention during active hostilities between the United States
and the Taliban and al Qaeda. Nothing in the text of the AUMF
or the National Defense Authorization Act suggests that a
change in the form of hostilities, if hostilities between the
relevant entities are ongoing, cuts off AUMF authorization. Cf.
Al-Bihani, 590 F.3d at 874 (rejecting petitioner’s argument that
“current hostilities are a different conflict” based on Taliban
shift from government to non-government form and noting
common sense and laws of war “do not draw such fine
distinctions”); Ali, 736 F.3d at 552 (acknowledging that “this
is a long war with no end in sight” but stating that “war against
al Qaeda, the Taliban, and associated forces obviously
continues” and detention authority under AUMF has no
statutory “time limit”). However characterized, the Executive
Branch represents, with ample support from record evidence,
that the hostilities described in the AUMF continue. In the
                               11
absence of a contrary Congressional command, that controls.
See Ludecke, 335 U.S. at 168–70 (deferring to political branch
determination that “war with Germany” persisted despite fact
that Germany had “surrender[ed]” and “Nazi Reich” had
“disintegrat[ed]”).

     Al-Alwi also argues that the United States’ entry into a
bilateral security agreement (Agreement) with Afghanistan
“mark[ed] the end of the original armed conflict” resulting in
Al-Alwi’s detention “and the commencement of a new one.”
Appellant’s Br. 33. In the Agreement, the United States
declared that its “forces shall not conduct combat operations in
Afghanistan.” Security and Defense Cooperation Agreement,
Afg.-U.S., Art. 2 ¶ 1, Sept. 30, 2014. Instead, the United States
agreed to “undertake supporting activities” to assist Afghan
security. Id. at Art. 2 ¶ 2. Al-Alwi contends that the United
States’ new role as a result of the Agreement changed the
“relevant conflict” and therefore the United States Government
has been divested of authority to detain him.

     But the Agreement does not declare an end to the conflict
on which Al-Alwi’s detention is based and the beginning of a
new one. Although the Agreement indicates that the United
States’ military operations in Afghanistan have changed, at the
same time it “acknowledge[s] that U.S. military operations to
defeat al-Qaida and its affiliates may be appropriate in the
common fight against terrorism.” Id. at Art. 2 ¶ 4. The
Agreement also contemplates “U.S. military counter-terrorism
operations.” Id. It does not declare an end to the conflict
resulting in Al-Alwi’s detention and the beginning of a
different one.

    “If the record establishes that United States troops are still
involved in active combat in Afghanistan,” detention of
“Taliban combatants” is “part of the exercise of ‘necessary and
                                12
appropriate force,’ and therefore [is] authorized by the
AUMF.” Hamdi, 542 U.S. at 521 (plurality opinion) (quoting
AUMF). The record so manifests here. Although United States
troops are involved in combat with a different operation name,
they nonetheless remain in active combat with the Taliban and
al Qaeda. Accordingly, the “relevant conflict” has not ended.
Id. The Government’s authority to detain Al-Alwi pursuant to
the AUMF has not terminated.

     C. Due process challenges and discovery request

     Al-Alwi raises three additional arguments on appeal. First,
he asserts that his continued detention, even if authorized by
the AUMF, violates substantive due process protections.
Second, he asserts that procedural due process requires more
procedural protections in future proceedings, including a
greater evidentiary burden of proof, than he has received so far.
Third, he asserts that the district court should have allowed
limited discovery on the differences between Operation
Enduring Freedom and Operation Freedom’s Sentinel.

     We do not reach the merits of these arguments, however,
because Al-Alwi forfeited them. Neither Al-Alwi’s habeas
petition nor his opposition to the Government’s motion to
dismiss mentioned any of these arguments. And Al-Alwi made
none of the claims at oral argument in district court. By not
asserting these arguments in the district court, Al-Alwi
forfeited them and we do not reach them. See Keepseagle v.
Perdue, 856 F.3d 1039, 1053 (D.C. Cir. 2017) (“issues and
legal theories not asserted” in district court “ordinarily will not
be heard on appeal” (internal quotation omitted)).

    For the foregoing reasons, the judgment of the district
court is affirmed.

                                                      So ordered.
