Opinion for the Court filed by Circuit Judge RUTH BADER GINSBURG.
Dissenting opinion filed by Circuit Judge CLARENCE THOMAS.
RUTH BADER GINSBURG, Circuit Judge:
This appeal concerns an interim regulation promulgated in urgent circumstances under the Food, Drug and Cosmetic Act, 21 U.S.C. §§ 301 et seq. (“FDC Act”). The regulation provides that the Food and Drug Administration (“FDA”) may permit Department of Defense (“DOD”) use of unapproved, investigational drugs on military personnel, in certain combat-related situations, without obtaining the service member’s informed consent. The setting for the case is the military operation known first as Desert Shield and, once hostilities commenced between the coalition forces and Iraq, as Desert Storm. Ruling dispositively within three weeks of the action’s commencement, the district court dismissed the complaint, which the plaintiffs attempted to bring on behalf of a class, on alternate grounds. See Doe v. Sullivan, 756 F.Supp. 12 (D.D.C.1991). First, the court held that the complaint questioned “a military decision that is not subject to judicial review.” Id. at 14. Alternately, the court rejected on the merits the statutory and constitutional challenges stated in the complaint.
Operation Desert Storm ended during the pendency of this appeal. The challenged FDA regulation, however, remains in place. Neither the DOD nor the FDA has proposed its withdrawal. The named plaintiffs therefore persist in urging adjudication of their facial challenge to the FDA’s regulation. They maintain, and we agree, that the controversy they press is one “capable of repetition, yet evading review.” While we further conclude that the consistency of the regulation with the governing law is justiciable, we agree with the district court that the regulation is within the FDA’s statutory authority under the FDC Act, and does not transgress any other legal constraint. For that reason, we affirm the order dismissing the complaint.
I. Background
On August 2, 1990, Iraq invaded Kuwait. In response, the United States deployed troops to Saudi Arabia as part of Operation Desert Shield and, under the mandate of the United Nations, began preparing for war. In addition to conventional arms, the Iraqi government had stockpiled a variety *113of chemical and biological warfare agents. Iraq had shown its willingness to employ these weapons by using them in the Iran-Iraq war of the 1980s and against Iraq’s own civilian Kurdish population. See Chemical and Biological Weapons Threat: The Urgent Need for Remedies, Hearings Before the Senate Comm, on Foreign Relations, 101st Cong., 1st Sess. 29, 31 (1989) (statement of Hon. William H. Webster, Director of Central Intelligence). The DOD therefore undertook a review of medical treatments that might be used to counter an Iraqi chemical and biological weapons attack. See Declaration of Edward D. Martin, M.D., Deputy Assistant Secretary of Defense (Professional Affairs and Quality Assurance) (“Martin Declaration”) at 2, reproduced in Joint Appendix (“J.A.”) at 32.
The DOD identified as useful against the Iraqi threat two investigational drugs which had not been approved by the FDA for the specific uses proposed.1 The FDC Act generally prohibits the use of unapproved drugs. See 21 U.S.C. § 355(a) (unapproved drugs may not be introduced into interstate commerce). Section 505(i) of the Act, 21 U.S.C. § 355(i), authorizes regulations exempting from the general prohibition unapproved drugs that are “intended solely for investigational use.” 2 Pursuant to that authorization, the FDA has promulgated regulations allowing investigational drugs “to be made available ... primarily for treatment use” in specified circumstances. See, e.g., 21 C.F.R. §§ 312.34, 312.35.
Section 505(i) of the FDC Act and FDA regulations generally require that the experts who administer investigational drugs first obtain from recipients their informed consent. See 21 U.S.C. § 355(i); 21 C.F.R. § 50.20 (1990).3 Exceptions are authorized *114when obtaining consent is deemed “not feasible.” See id. The consent waiver regulation in effect at the start of Operation Desert Shield required both the drug investigator and an independent physician to certify that the drug recipient was physically or mentally unable to give effective consent, and that there was insufficient time to get consent from a legal representative.4
After identifying the two investigational drugs it wished to use in Operation Desert Shield, the DOD concluded that obtaining informed consent in the heat of imminent or ongoing combat would not be practicable. In battlefield situations, the DOD maintained, “[i]f a soldier’s life will be endangered by nerve gas ... it is not acceptable from a military standpoint to defer to whatever might be the soldier’s personal preference” for treatment. 55 Fed.Reg. 52,814, 52,815 (1990) (Letter from DOD’s Assistant Secretary of Defense (Health Affairs) (October 30, 1990) to Department of Health and Human Services Assistant Secretary for Health). The safety of other personnel in a soldier's unit and the accomplishment of the combat mission, the DOD urged, warranted mandatory use of investigational drugs.
The combat-ready personnel, whom DOD wanted to treat with the investigational drugs prior to any exposure to nerve gas or biological warfare, did not fit within the existing regulatory exception from informed consent requirements. The DOD therefore sought, and the FDA adopted, a regulatory change. On December 21,1990, the FDA promulgated Rule 23(d) as an interim regulation. See 55 Fed.Reg. 52,817 (to be codified at 21 C.F.R. § 50.23(d)). Rule 23(d) permits “the Commissioner of Food and Drugs to make the determination that obtaining informed consent from military personnel for the use of an investigational drug or biologic is not feasible in certain battlefield or combat-related situations.” See id. at 52,814.5
*115Rule 23(d) sets exacting conditions for waivers of informed consent. The DOD’s request for a waiver “must be limited to a specific military operation involving combat or the immediate threat of combat.” 55 Fed.Reg. at 52,817 (to be codified at 21 C.F.R. § 50.23(d)(1)). The DOD must include in the request written justification for the conclusions of the responsible DOD physicians and drug investigators that the requisite military combat exigency exists. The request must also affirm that an institutional review board has approved the use of the investigational drug without informed consent. See id. The FDA, prior to granting a requested waiver, must evaluate the risks and benefits of the investigational drug in the circumstances of the use proposed by the DOD. See 55 Fed.Reg. 52,817 (to be codified at 21 C.F.R. § 50.23(d)(2)). The FDA may grant a waiver, i.e., rule that informed consent is not feasible, “only when withholding treatment would be contrary to the best interests of the military personnel and there is no available satisfactory alternative therapy.” 55 Fed.Reg. 52,817 (to be codified at 21 C.F.R. § 50.23(d)(1)). Waivers expire after one year, but they may be renewed. Based on changed circumstances, a waiver may be terminated by the DOD or the FDA before the year is up. See 55 Fed.Reg. 52,817 (to be codified at 21 C.F.R. § 50.23(d)(4)).
On December 31, 1990, and January 8, 1991, in response to DOD requests, the FDA issued waiver rulings under Rule 23(d). Those rulings determined that obtaining informed consent was not feasible, because of military combat exigencies in Operation Desert Shield, for the use of two investigational drugs, a nerve gas pretreatment and a botulism poisoning preventative. See supra note 1.
Doe, a serviceman stationed in Saudi Arabia, brought this action on January 11, 1991. His wife, suing derivatively, joined him as co-plaintiff. Proceeding under a fictitious name, and invoking Rule 23(b)(2) of the Federal Rules of Civil Procedure, Doe sought to represent a class consisting of “all United States military personnel who are or will be serving in Operation Desert Shield in Saudi Arabia, Kuwait, or Iraq.” Complaint for Declaratory and Injunctive Relief para. 31. Doe’s complaint presented three claims for relief; each claim was stated first on behalf of the named plaintiffs, and then repeated on behalf of the class. First, Doe challenged Rule 23(d) on its face as outside the authority Congress granted to the FDA under section 505(i) of the FDC Act, 21 U.S.C. § 355(i). Second, Doe charged that the *116DOD’s use of unapproved investigational drugs, under FDA Rule 23(d) permission but without obtaining the informed consent of the subject, could not be reconciled with the informed consent direction contained in section 1401(c)(1) of the 1985 Defense Department Authorization Act, Pub.L. No. 98-525, 98 Stat. 2492, 2615 (1984) (codified at 10 U.S.C. § 980).6 Third, Doe alleged that the government’s use of drugs on a nonconsenting person constitutes a substantial deprivation of that person’s liberty and therefore violates the due process clause of the Fifth Amendment.
The district court dismissed Doe’s action on January 31, 1991, twenty days after the complaint was filed and seventy days short of the time allowed for a motion to certify an alleged class. See D.D.C. Local Rule 203(b) (motion for certification due “[w]ithin 90 days after the filing of a complaint”). Since the date of the district court’s final order, the United States and its allies have fought and defeated Iraq. At midnight, February 27,1991, President Bush declared a ceasefire. On March 15, 1991, the DOD formally notified the FDA that the military operation creating the need for use of the two drug products without informed consent had ended. Under the terms of Rule 23(d)(4), see supra note 5, this notice terminated the waivers of informed consent. That same day, the government moved to dismiss this appeal as moot. We set out next our reasons for concluding that the claim Doe continues to pursue — his facial challenges to the FDA’s Rule 23(d) — is not moot.
II. Mootness
Article III of the Constitution allows federal courts to adjudicate only “actual, ongoing controversies.” Honig v. Doe, 484 U.S. 305, 317, 108 S.Ct. 592, 600, 98 L.Ed.2d 686 (1988). An appellate court, operating under this constraint, may not rule on a case which, although live when brought in the district court, has been rendered academic by later events. See Clarke v. United States, 915 F.2d 699, 701 (D.C.Cir.1990) (en banc).
The end of the war against Iraq, and the attendant termination of the informed consent waivers geared to that conflict, have rendered moot Doe’s endeavor to block implementation of the December 31, 1990, and January 8, 1991, specific applications of the FDA’s Rule 23(d). See supra p. 1374. Doe so concedes, but he maintains that the case remains live. Doe contrasts the now withdrawn consent waivers, i.e., the two specific applications of Rule 23(d), with the continuing vitality of the Rule itself, and he asserts that his facial challenge to Rule 23(d) warrants adjudication.7 Doe invokes the exception to the mootness doctrine for controversies “capable of repetition, yet evading review.” Southern Pacific Terminal Co. v. ICC, 219 U.S. 498, 515, 31 S.Ct. 279, 283, 55 L.Ed. 310 (1911). The very fact that the DOD seeks to retain Rule 23(d) as a rule continuing indefinitely in force,8 Doe urges, supports his conten*117tion that recurrence of the issue underlying his claim is plausibly projected. See Appellants’ Response to the Motion of Secretary of Defense and Secretary of Health and Human Services to Dismiss Appeal as Moot at 5. Compare City of New Haven v. United States, 809 F.2d 900, 904-05 (D.C. Cir.1987) and Better Government Ass’n v. Department of State, 780 F.2d 86, 91-92 (D.C.Cir.1986) (facial challenges entertained when regulation remained effective, despite mootness of specific applications) with Clarke v. United States, 915 F.2d at 704-05 (case declared moot when challenged legislative direction expired, and reenactment by Congress appeared extremely unlikely).
If “(1) the challenged action was in its duration too short to be fully litigated prior to its cessation or expiration, and (2) there [is] a reasonable expectation that the same complaining party [will] be subjected to the same action again,” then the controversy is “capable of repetition, yet evading review.” Weinstein v. Bradford, 423 U.S. 147, 149, 96 S.Ct. 347, 349, 46 L.Ed.2d 350 (1975) (per curiam). We now consider whether this case fits that bill.
The “evading review” standard, we conclude, is securely satisfied here, and our dissenting colleague does not quarrel with that conclusion. The consent waivers granted by the FDA for Desert Shield were withdrawn within three months. Rule 23(d) limits waivers, if not earlier terminated or renewed at the DOD’s request, to terms of one year. See 55 Fed.Reg. 52,817 (to be codified at 21 C.F.R. § 50.23(d)(4)).
Orders of considerably longer duration have been held to evade review. See First National Bank of Boston v. Bellotti, 435 U.S. 765, 774, 98 S.Ct. 1407, 1414, 55 L.Ed.2d 707 (1978) (eighteen months too short for full litigation); Southern Pacific Terminal Co., 219 U.S. at 514-16, 31 S.Ct. at 283-84 (order that expires by its terms after two years evades review); In re Reporters Comm. for Freedom of the Press, 773 F.2d 1325, 1329 (D.C.Cir.1985) (issue evades review when controversy endures less than two years).9
We are mindful, too, of a notice concern advanced by Doe. Under Rule 23(d), the DOD need not make public its requests for waivers of informed consent, and the FDA need not make public its determinations on DOD requests. Military personnel therefore may have no opportunity to institute litigation prior to the time an experimental drug is administered. Thus, both the uncertain starting time for a challenge to a specific application of Rule 23(d), and the generally short-term (one-year) character of the waivers authorized by the Rule,10 convince us that the action Rule 23(d) authorizes evades review.
Turning to the “capable of repetition” requirement, we are reminded by the government of this statement in Clarke, 915 F.2d at 704: “In estimating the likelihood of an event’s occurring in the future, a natural starting point is how often it has *118occurred in the past.” The government “point[s] out in this regard that in the nearly 30 years that Section 505(i) of the FDC Act has imposed a general requirement of informed consent, the recent conflict with Iraq has been the only occasion in which DOD has found that military exigencies might require the administration of investigational drugs without informed consent.” Motion of Secretary of Defense and Secretary of Health and Human Services to Dismiss Appeal as Moot at 9-10 (emphasis in original).
Official reports indicate, however, that conditions changed ominously in the 1980s. In very recent years, the global spread of chemical and biological weapons has become a matter of grave concern to national defense planners. See generally E. Spiers, Chemical Weaponry: A Continuing Chau lenge 126-57 (1989) (prospects for chemical warfare and assessment of modern chemical weaponry). See also Statement by President on Chemical Weapons Initiative, 27 Weekly Comp. Pres. Doc. 599 (May 13, 1991) (“The Gulf war has once again raised the specter of chemical weapons and demonstrated that unscrupulous regimes can and will threaten innocent populations with these weapons of terror so long as we permit them to exist.”).11 We set out here illustrative warnings.
In 1989 Senate testimony, Judge William H. Webster, Director, Central Intelligence Agency, addressed “the very serious problem of the proliferation of chemical and biological weapons.” Hearings on Global Spread of Chemical and Biological Weapons Before the Senate Comm, on Governmental Affairs and Perm. Subcomm. on Investigations, 101st Cong., 1st Sess. 10 (1989) (“Chemical Weapons Hearings ”). Judge Webster estimated that “at least 20 countries” had chemical weapons, id. at 18; he anticipated that the disturbing trend would continue “despite ongoing multi-lateral efforts to stop the[] proliferation.” Id. at 10. “At least 10 countries,” he further stated, “are working to produce both previously known and futuristic biological weapons.” Id. Judge Webster listed, among nations that commenced large-scale production and stockpiling of chemical warfare agents in the 1980s: Iraq, Syria, Iran, and Libya. Id. at 11-13. See also Harris, Chemical Weapons Proliferation in the Developing World, in Rusi and Brassey’s Defense Yearbook 1989, at 67-88 (1989), reprinted in Chemical Weapons Hearings at 608-29.
A 1990 Army report observed: “Chemical weapons are rapidly becoming low cost weapons of mass destruction for poorer nations. These weapons are neither difficult nor expensive to produce. The Iraqi and Iranian use of chemicals in the Gulf War is likely to encourage other combatants to use these weapons.” M. Stone & C. Vuono, Trained and Ready in an Era of Change: The Posture of the United States Army, Fiscal Year 1991, reprinted in Department of Defense Appropriations for 1991: Hearings Before a Sub-comm. of the House Comm, on Appropriations, 101st Cong., 2d Sess. 931 (1990) {“DOD Appropriations Hearings ”). The Secretary of Defense, in his Annual Report to the President and Congress, January 1990, cautioned: “[G]iven the attractiveness of chemical weapons to Third World countries, the United States must be able to deter the use of chemical weapons against our forces.” DOD Appropriations Hearings at 163. The Marine Corps, in 1990, requested an additional 52,555 protective masks “to survive and continue to operate” in a contaminated environment, noting that the “threat is formidable.” Id. at 771-72. See also D. Cheney, Annual Report of the Secretary of Defense to the President and Congress, January 1991, at 3 (“Proliferation of nuclear, chemical, and biological weapons and the missile technology for long-range delivery systems will make regional conflict increasingly destructive and lethal.”); id. at 6 (“Third world nations in pursuit of nuclear, chemi*119cal, or biological weapons technology ... pose a serious threat.”); id. at 65 (Marine Corps reports need for improved nuclear, biological, and chemical defense equipment).12
Doe, though among the troops brought safely home, remains a soldier in the service of the United States, subject to assignment wherever his country needs him. In common with the class he sought to represent, see supra pp. 115-16, he originally had, and has not lost, a “personal stake” in this case. Cf. United States Parole Commission v. Geraghty, 445 U.S. 388, 400 n. 7, 100 S.Ct. 1202, 1210 n. 7, 63 L.Ed.2d 479 (1980). Based on Doe’s past exposure to the threat of chemical warfare in Saudi Arabia, and his continuing status as a member of our armed forces, we conclude that he confronts a risk of DOD recourse to Rule 23(d) sufficient to satisfy the “capable of repetition” test.13 We reach this *120conclusion cognizant of the still. undiminished, worldwide chemical and biological weapons threat, the hardly hypothetical danger chemical warfare agents pose for combat troops, and the DOD’s apparent determination to retain Rule 23(d) in place so that, if need be, it may again gain expeditious approval for the use of experimental drugs without informed consent.14
We recognize as well “the flexible character of the Article] III mootness doctrine” developed in Supreme Court guidepost decisions. See Geraghty, 445 U.S. at 400, 100 S.Ct. at 1211. It is enough, in a case of this order, that the litigant “faces some likelihood of becoming involved in the same controversy in the future.” Id. at 398, 100 S.Ct. at 1209. The core decision is “whether the controversy is capable of repetition and not ... whether the claimant ha[s] demonstrated that a recurrence of the dispute [is] more probable than not.” Honig v. Doe, 484 U.S. at 318 n. 6, 108 S.Ct. at 601 n. 6 (emphasis in original).
The government argues that Doe’s challenge is either too late or too early: moot because Operation Desert Storm is over; not ripe, because the next conflict is not yet upon us. Under these tight lines, it appears, Doe and other soldiers similarly situated could litigate Rule 23(d)’s consistency with the governing law only when a military crisis occurs, and a prolonged one at that, hardly a prime time for dispassionate adjudication. While combat is imminent or ongoing, moreover, the government might raise a justiciability objection of a different kind. See infra, Part III.
Given the Supreme Court’s instruction to apply the “reasonable expectation” standard without excessive “stringency,” see Honig v. Doe, 484 U.S. at 318 n. 6, 108 S.Ct. at 602 n. 6, we note this prudential consideration. Congress, not this court, is the ultimate arbiter of the compatibility of Rule 23(d) with the legislature’s will. Both this court, on judicial review of a case commenced when combat was imminent, and Congress, in determining the need, if any, for legislative change in the wake of the Desert Storm experience, can consider the question Doe tenders most calmly and effectively after the battle fire is extinguished and before it is rekindled.
III. Amenability to Judicial Review
The district court, although it ruled, conditionally, that Doe’s complaint lacked legal merit, held, initially, that Doe’s claims were not amenable to judicial review. Only the electoral branches — Congress and the President — that court indicated, are competent authorities in matters of military disci*121pline and strategy. With respect to Doe’s challenge to the PDA’s authority to promulgate Rule 23(d), the district judge noted:
Plaintiffs’ claim against the Secretary of Health and Human Services regarding the FDA’s interim rule arguably does not implicate military discipline and strategy. Whether the fact that the interim rule was adopted at the DOD’s request in preparing for possible war insulates it from the ordinary scope of judicial review is not clear. However, Congress delegated rulemaking authority regarding unapproved drugs to the FDA, which is part of the executive branch. 21 U.S.C. § 355(i). The FDA exercised that delegated authority in adopting § 50.23(d). The Supreme Court has cast the principle of judicial deference to the electoral branches in military matters in broad terms. See, e.g., Chappell v. Wallace, 462 U.S. 296, 103 S.Ct. 2362 [76 L.Ed.2d 586] (1983); Gilligan v. Morgan, 413 U.S. 1, 93 S.Ct. 2440 [37 L.Ed.2d 407] (1973). On balance, therefore, the Court believes that [Rule 23(d) ] is not reviewable.
Doe v. Sullivan, 756 F.Supp. at 15 n. 2. We agree that deference is owed to the political branches in military matters, but do not agree that judicial review of the matter here at issue is out of order.
In contrast to the turbulent background of this litigation, Doe’s facial challenge to Rule 23(d) is a straightforward one with a commonplace cast. Doe contends that, in promulgating Rule 23(d), the FDA stepped outside its statutory authority and adopted an exception to its informed consent regulations that is “not in accordance with law.” Doe therefore seeks a court order setting aside the FDA’s action. See 5 U.S.C. § 706(2)(A), (C) (court shall set aside agency action that is “not in accordance with law” or is “in excess of statutory jurisdiction, authority, or limitations”). We see no “military action” bar to the brand of review Doe now requests.15
From the main rule that administrative acts are reviewable in court on the complaint of a person adversely affected within the meaning of a relevant statute (here, principally the informed consent provision in section 505(i) of the FDC Act), the Administrative Procedure Act (APA) excepts, inter alia, “military authority exercised in the field in time of war or in occupied territory.” 5 U.S.C. § 701(b)(1)(G). The government emphasizes that exception. See Brief for Appellees at 16, 24, 29. We think the “military authority” exception is not on point.
Doe currently does not ask us to review military commands made in combat zones or in preparation for, or in the aftermath of, battle. His claim, as now advanced, entails no judicial interference with the relationship between soldiers and their military superiors. Cf. Chappell v. Wallace, 462 U.S. 296, 300, 103 S.Ct. 2362, 2365, 76 L.Ed.2d 586 (1983) (court will “hesitate long” before interfering in relationship between military personnel and their superior officers); Gilligan v. Morgan, 413 U.S. 1, 10, 93 S.Ct. 2440, 2445, 37 L.Ed.2d 407 (1973) (court is not well-positioned to interfere in composition, training, equipping, and control of military force). We confront at this time not a dispute over military strategy or discipline, not one between soldiers and their superiors, but one over the scope of the authority Congress has entrusted to the FDA. Homing in on the facial challenge to the FDA’s regulation, Doe’s counsel explained:
Plaintiffs seek review under the Administrative Procedure Act ... of a rule published in the Federal Register by the Secretary of HHS, who is not part of any military chain of command____ [W]hen he adopted the rule, [the Secretary] did not purport to be exercising the President’s powers as Commander in Chief. Rather, he relied exclusively on his au*122thority under the Food, Drug, and Cosmetic Act, ... a statute which cannot, by any stretch of the imagination, be construed as a source of authority for “military discipline.”
Reply Brief at 2-3. That explanation accurately portrays Doe’s APA claim.
The FDA’s Rule 23(d), we recognize, unquestionably involves a military matter: it allows the FDA to grant the Department of Defense a waiver of informed consent requirements in certain battlefield or combat-related situations. But the judgment Doe asks the court to make does not entail judicial review of the existence of a military exigency. Rather, Doe’s facial attack asks simply whether the law that governs FDA action permits the measure which that non-military agency has taken. The question thus presented is meet for judicial review,16 and we proceed to its resolution.
IV. Merits
On the issue ultimately dispositive of this appeal, we are in accord with the district court: the FDA’s Rule 23(d), we hold, is within that agency’s rulemaking authority under the governing section of the FDC Act, and is not barred by the 1985 Department of Defense Authorization Act or the due process clause of the Fifth Amendment. See Doe v. Sullivan, 756 F.Supp. at 15-18.
A. The FDC Act
We review the FDA’s interpretation of the FDC Act under the two-step formulation restated in Chevron U.S.A. v. Natural Resources Defense Council, 467 U.S. 837, 104 S.Ct. 2778, 81 L.Ed.2d 694 (1984). See, e.g., E.R. Squibb and Sons, Inc. v. Bowen, 870 F.2d 678, 680-81 (D.C.Cir.1989). First, if “the intent of Congress is clear,” then “the court as well as the agency, must give effect to the unambiguously expressed intent of Congress.” Chevron, 467 U.S. at 842-43, 104 S.Ct. at 2781-82. Our decisions call this initial step “Chevron I” analysis. See Coal Employment Project v. Dole, 889 F.2d 1127, 1131 (D.C.Cir.1989). If, however, the governing legislation is “silent or ambiguous with respect to the specific issue,” the court generally need ask only whether the agency’s interpretation is a “permissible construction of the statute.” Chevron, 467 U.S. at 843, 104 S.Ct. at 2782. Circuit precedent labels this “Chevron II” analysis. See Coal Employment Project, 889 F.2d at 1131.
Doe urged in the district court, and maintains on appeal, that Congress spoke plainly in the FDC Act and that the FDA failed to give effect to the unambiguously expressed legislative intent; in other words, Doe contends that the FDA’s Rule 23(d) must fail under Chevron I inspection. We now examine that contention.
Congress provided, in section 505(i) of the FDC Act, for the use of unapproved investigational drugs only on the informed *123consent of the human subjects affected, “except where [the experts administering the drug] deem [the human subject’s consent] not feasible.” 21 .U.S.C. § 355(i).17 The words “not feasible” in this context, Doe insists, focus on the human recipient of the drug: if that individual has the capacity intelligently to give or withhold consent, then the exception cannot apply; if, on the other hand, that individual is unable intelligently to convey a choice, only then is informed consent “not feasible” so that the decision may be made by the experts administering the drug.
Doe observes that, before the FDA adopted Rule 23(d), the agency itself apparently subscribed to Doe’s view, i.e., Rule 23 formerly recognized consent as “not feasible” only where the human subject could not competently make or convey an informed choice. See 21 C.F.R. § 50.23(a), (b), set out supra note 4. Doe additionally cites, as supportive of his position, remarks by legislators pointing to the “not feasible” language. See 108 Cong.Rec. 22,042-43 (remarks of Sen. Kefauver and Sen. Javits).
In common with the district court, we do not find the text of FDC Act section 505(i) free from ambiguity. The FDA currently reads “not feasible” to include “impracticable,” taking into account particularly urgent circumstances: a combat-zone setting, the safety of military personnel at that location, and the compelling need to promote success of the service members’ mission. That reading, as the district court said, “is well within the ordinary meaning” of the words Congress used. See Doe v. Sullivan, 756 F.Supp. at 16.
We note, furthermore, that the statutory section in question emphasizes the professional judgment of the experts responsible for administering the unapproved investigational new drugs to human subjects; the legislative text permits exceptions “where [those experts] deem [consent] not feasible.” See 21 U.S.C. § 355(i). Correspondingly, Rule 23(d) requires written justification for the conclusions of the drug investigators and physicians responsible for the medical care of the troops involved, as well as the approval of an institutional review board.
While it is true that the FDA’s prior interpretation of the words “not feasible” focused on the subject’s condition, the agency here has not reversed course. It has simply added a tightly circumscribed set of urgent circumstances in which the main rule of informed consent, with fidelity to the statute’s terms, can be displaced. Cf. Rust v. Sullivan, — U.S. -, 111 S.Ct. 1759, 1769, 114 L.Ed.2d 233 (1991) (agency’s revised interpretation of a statute, if supported by a “reasoned analysis,” is entitled to deference). As for the legislative history, the Senate floor statements Doe has called to our attention are scarcely helpful. They merely repeat the statutory language, and therefore do not advance our understanding of the legislators’ intent.
The FDA’s Rule 23(d), we thus conclude, reasonably construes a statute that leaves room for interpretation. We therefore defer to the agency’s determination.18
B. The Defense Authorization Act
In support of his contention that Rule 23(d) is facially invalid under the De*124fense Authorization Act (“DAA”), Doe highlights this language from 10 U.S.C. § 980: “Funds appropriated to the Department of Defense may not be used for research involving a human being as an experimental subject unless [] the informed consent of the subject is obtained in advance.” 19 We are satisfied that the DAA does not block the FDA action in question. Rule 23(d) authorizes the Commissioner of Food and Drugs to make certain determinations upon the request of the Assistant Secretary of Defense. The DAA, however, limits the authority of the Department of Defense, not the authority of the Food and Drug Commissioner. Although it might be argued that the DAA restricts the authority of the Assistant Secretary of Defense to make the request anticipated by Rule 23(d), it cannot be argued that the DAA restricts the Secretary of Health and Human Services from promulgating Rule 23(d). Nor can it be argued that an FDC regulation is capable of conferring on the Secretary of Defense a power that, as Doe maintains, a statute (the Defense Authorization Act) expressly prohibits. Accordingly, we reject Doe’s claim that Rule 23(d) is facially invalid under the DAA.
C. The Fifth Amendment Due Process Clause
In most circumstances, as Doe observes, the Constitution’s due process guarantee protects an individual’s liberty to decide whether or not to submit to serious medical treatment. See, e.g., Washington v. Harper, 494 U.S. 210, 110 S.Ct. 1028, 1036-37, 108 L.Ed.2d 178 (1990). In mounting a facial challenge, however, Doe’s burden is heavy: he must demonstrate that no possible application of Rule 23(d) can be squared with the Fifth Amendment. See National Treasury Employees Union v. Yeutter, 918 F.2d 968, 975 (D.C.Cir.1990). The very application of Rule 23(d) in Operation Desert Storm, we point out, belies Doe’s contention. As the district court stated, two concerns stressed by the DOD “constitute legitimate government interests that ... counterbalance an individual’s interest in being free from experimental treatment without giving informed consent.” Doe v. Sullivan, 756 F.Supp. at 17. First, “administering the drugs uniformly prevents unnecessary danger to troops and medical personnel from injury to, or the death of, fellow military personnel in battle. [Also,] the DOD ha[d] an interest in successfully accomplishing the military goals of Operation Desert Storm.” Id. We agree with the district court that these considerations rendered compatible with due process the invocation of Rule 23(d) in that particular combat situation. Conceivably, Rule 23(d) might at some future time be applied in violation of the Fifth Amendment; this single constitutionally valid application of the Rule, however, is all that is needed to defeat Doe’s facial constitutional challenge.
Conclusion
(1) Soldier Doe’s complaint retains vitality to the extent that it presents a facial challenge to the legality of the FDA’s Rule 23(d). That challenge describes a controversy capable of repetition, yet evading review; it therefore survives inspection for mootness. (2) The complaint, reduced to the claim that FDA Rule 23(d), on its face, is inconsistent with the governing law, is justiciable. (3) Rule 23(d) is a permissible construction of section 505(i) of the FDC Act and is not otherwise unlawful; we therefore defer to the FDA’s decision to promulgate the rule.
For the reasons stated, the dismissal of Doe’s complaint is
Affirmed.