20

Authority to Use Military Force in Libya

The President had the constitutional authority to direct the use of military force in Libya 

because he could reasonably determine that such use of force was in the national interest.

Prior congressional approval was not constitutionally required to use military force in the 

limited operations under consideration. 

April 1, 2011

MEMORANDUM OPINION FOR THE ATTORNEY GENERAL

This memorandum memorializes advice this Office provided to you, 

prior to the commencement of recent United States military operations in 

Libya, regarding the President’s legal authority to conduct such operations. For the reasons explained below, we concluded that the President 

had the constitutional authority to direct the use of force in Libya because 

he could reasonably determine that such use of force was in the national 

interest. We also advised that prior congressional approval was not constitutionally required to use military force in the limited operations under 

consideration.

I.

In mid-February 2011, amid widespread popular demonstrations seeking governmental reform in the neighboring countries of Tunisia and 

Egypt, as well as elsewhere in the Middle East and North Africa, protests 

began in Libya against the autocratic government of Colonel Muammar 

Qadhafi, who has ruled Libya since taking power in a 1969 coup. Qadhafi 

moved swiftly in an attempt to end the protests using military force. Some 

Libyan government officials and elements of the Libyan military left the 

Qadhafi regime, and by early March, Qadhafi had lost control over much 

of the eastern part of the country, including the city of Benghazi. The 

Libyan government’s operations against its opponents reportedly included 

strafing of protesters and shelling, bombing, and other violence deliberately targeting civilians. Many refugees fled to Egypt and other neighboring countries to escape the violence, creating a serious crisis in the region.

On February 26, 2011, the United Nations Security Council (“UNSC”) 

unanimously adopted Resolution 1970, which “[e]xpress[ed] grave con-
Authority to Use Military Force in Libya

21

cern at the situation in the Libyan Arab Jamahiriya,” “condemn[ed] the 

violence and use of force against civilians,” and “[d]eplor[ed] the gross 

and systematic violation of human rights” in Libya. S.C. Res. 1970, U.N. 

Doc. S/RES/1970 (Feb. 26, 2011); Press Release, Security Council, In 

Swift, Decisive Action, Security Council Imposes Tough Measures on 

Libyan Regime, Adopting Resolution 1970 in Wake of Crackdown on 

Protesters, U.N. Press Release SC/10187/Rev. 1 (Feb. 26, 2011). The 

resolution called upon member states, among other things, to take “the 

necessary measures” to prevent arms transfers “from or through their 

territories or by their nationals, or using their flag vessels or aircraft”; to 

freeze the assets of Qadhafi and certain other close associates of the 

regime; and to “facilitate and support the return of humanitarian agencies 

and make available humanitarian and related assistance” in Libya. S.C. 

Res. 1970, ¶¶ 9, 17, 26. The resolution did not, however, authorize members of the United Nations to use military force in Libya.

The Libyan government’s violence against civilians continued, and 

even escalated, despite condemnation by the UNSC and strong expressions of disapproval from other regional and international bodies. See, 

e.g., African Union, Communique of the 265th Meeting of the Peace and 

Security Council, PSC/PR/COMM.2(CCLXV) (Mar. 10, 2011) (describing the “prevailing situation in Libya” as “pos[ing] a serious threat to 

peace and security in that country and in the region as a whole” and 

“[r]eiterat[ing] AU’s strong and unequivocal condemnation of the indiscriminate use of force and lethal weapons”); News Release, Organization 

of the Islamic Conference, OIC General Secretariat Condemns Strongly 

the Excessive Use of Force Against Civilians in the Libyan Jamahiriya

(Feb. 22, 2011), http://www.oic-oci.org/topic_detail.asp?t_id=4947&x_

key= (last visited ca. Apr. 2011) (reporting that “the General Secretariat 

of the Organization of the Islamic Conference (OIC) voiced its strong 

condemnation of the excessive use of force against civilians in the Arab 

Libyan Jamahiriya”). On March 1, 2011, the United States Senate passed 

by unanimous consent Senate Resolution 85. Among other things, the 

Resolution “strongly condemn[ed] the gross and systematic violations of 

human rights in Libya, including violent attacks on protesters demanding 

democratic reforms,” “call[ed] on Muammar Gadhafi to desist from 

further violence,” and “urge[d] the United Nations Security Council to 

take such further action as may be necessary to protect civilians in Libya 
35 Op. O.L.C. 20 (2011)

22

from attack, including the possible imposition of a no-fly zone over Libyan territory.” S. Res. No. 112-85, §§ 2, 3, 7 (as passed by Senate, Mar. 1, 

2011). On March 12, the Council of the League of Arab States similarly 

called on the UNSC “to take the necessary measures to impose immediately a no-fly zone on Libyan military aviation” and “to establish safe 

areas in places exposed to shelling as a precautionary measure that allows 

the protection of the Libyan people and foreign nationals residing in 

Libya, while respecting the sovereignty and territorial integrity of neighboring States.” League of Arab States, The Outcome of the Council of the 

League of Arab States Meeting at the Ministerial Level in Its Extraordinary Session on the Implications of the Current Events in Libya and the 

Arab Position, Res. No. 7360, ¶ 1 (Mar. 12, 2011).

By March 17, 2011, Qadhafi’s forces were preparing to retake the city 

of Benghazi. Pledging that his forces would begin an assault on the city 

that night and show “no mercy and no pity” to those who would not give 

up resistance, Qadhafi stated in a radio address: “We will come house by 

house, room by room. It’s over. The issue has been decided.” Dan 

Bilefsky & Mark Landler, Military Action Against Qaddafi Is Backed by 

U.N., N.Y. Times, Mar. 18, 2011, at A1. Qadhafi, President Obama later 

noted, “compared [his people] to rats, and threatened to go door to door 

to inflict punishment. . . . We knew that if we . . . waited one more day, 

Benghazi, a city nearly the size of Charlotte, could suffer a massacre that 

would have reverberated across the region and stained the conscience of 

the world.” Press Release, Office of the Press Secretary, The White 

House, Remarks by the President in Address to the Nation on Libya 

(Mar. 28, 2011) (“March 28, 2011 Address”), http://www.whitehouse.

gov/the-press-office/2011/03/28/remarks-president-address-nation-libya

(last visited ca. Apr. 2014).

Later the same day, the UNSC addressed the situation in Libya again 

by adopting, by a vote of 10-0 (with five members abstaining), Resolution 

1973, which imposed a no-fly zone and authorized the use of military 

force to protect civilians. See S.C. Res. 1973, U.N. Doc. S/RES/1973 

(Mar. 17, 2011); Press Release, Security Council, Security Council Approves ‘No-Fly Zone’ Over Libya, Authorizing ‘All Necessary Measures’ 

to Protect Civilians, by Vote of 10 in Favour with 5 Abstentions, U.N. 

Press Release SC/10200 (Mar. 17, 2011). In this resolution, the UNSC 

determined that the “situation” in Libya “continues to constitute a threat 
Authority to Use Military Force in Libya

23

to international peace and security” and “demand[ed] the immediate 

establishment of a cease-fire and a complete end to violence and all attacks against, and abuses of, civilians.” S.C. Res. 1973. Resolution 1973 

authorized member states, acting individually or through regional organizations, “to take all necessary measures . . . to protect civilians and civilian populated areas under threat of attack in the Libyan Arab Jamahiriya, 

including Benghazi, while excluding a foreign occupation force of any 

form on any part of Libyan territory.” Id. ¶ 4. The resolution also specifically authorized member states to enforce “a ban on all [unauthorized] 

flights in the airspace of the Libyan Arab Jamahiriya in order to help 

protect civilians” and to take “all measures commensurate to the specific 

circumstances” to inspect vessels on the high seas suspected of violating 

the arms embargo imposed on Libya by Resolution 1970. Id. ¶¶ 6–8, 13.

In remarks on March 18, 2011, President Obama stated that, to avoid 

military intervention to enforce Resolution 1973, Qadhafi needed to: 

implement an immediate ceasefire, including by ending all attacks on 

civilians; halt his troops’ advance on Benghazi; pull his troops back 

from three other cities; and establish water, electricity, and gas supplies 

to all areas. Press Release, Office of the Press Secretary, The White 

House, Remarks by the President on the Situation in Libya (Mar. 18, 

2011) (“March 18, 2011 Remarks”), http://www.whitehouse.gov/thepress-office/2011/03/18/remarks-president-situation-libya (last visited 

ca. Apr. 2011). The President also identified several national interests 

supporting United States involvement in the planned operations:

Now, here is why this matters to us. Left unchecked, we have every 

reason to believe that Qaddafi would commit atrocities against his 

people. Many thousands could die. A humanitarian crisis would ensue. The entire region could be destabilized, endangering many of 

our allies and partners. The calls of the Libyan people for help would 

go unanswered. The democratic values that we stand for would be 

overrun. Moreover, the words of the international community would 

be rendered hollow.

Id. President Obama further noted the broader context of the Libyan 

uprising, describing it as “just one more chapter in the change that is 

unfolding across the Middle East and North Africa.” Id.
35 Op. O.L.C. 20 (2011)

24

Despite a statement from Libya’s Foreign Minister that Libya would 

honor the requested ceasefire, the Libyan government continued to conduct offensive operations, including attacks on civilians and civilianpopulated areas. See Press Release, Office of the Press Secretary, The 

White House, Letter from the President Regarding Commencement of 

Operations in Libya: Text of a Letter from the President to the Speaker of 

the House of Representatives and the President Pro Tempore of the Senate (Mar. 21, 2011) (“March 21, 2011 Report to Congress”), http://www.

whitehouse.gov/the-press-office/2011/03/21/letter-president-regardingcommencement-operations-libya (last visited ca. Apr. 2011). In response, 

on March 19, 2011, the United States, with the support of a number of its 

coalition partners, launched airstrikes against Libyan targets to enforce 

Resolution 1973. Consistent with the reporting provisions of the War

Powers Resolution, 50 U.S.C. § 1543(a) (2006), President Obama provided a report to Congress less than forty-eight hours later, on March 21, 

2011. The President explained:

At approximately 3:00 p.m. Eastern Daylight Time, on March 19, 

2011, at my direction, U.S. military forces commenced operations to 

assist an international effort authorized by the United Nations (U.N.) 

Security Council and undertaken with the support of European allies 

and Arab partners, to prevent a humanitarian catastrophe and address 

the threat posed to international peace and security by the crisis in 

Libya. As part of the multilateral response authorized under U.N. 

Security Council Resolution 1973, U.S. military forces, under the 

command of Commander, U.S. Africa Command, began a series of 

strikes against air defense systems and military airfields for the purposes of preparing a no-fly zone. These strikes will be limited in 

their nature, duration, and scope. Their purpose is to support an international coalition as it takes all necessary measures to enforce the 

terms of U.N. Security Council Resolution 1973. These limited U.S. 

actions will set the stage for further action by other coalition partners.

March 21, 2011 Report to Congress. The report then described the background to the strikes, including UNSC Resolution 1973, the demand for a 

ceasefire, and Qadhafi’s continued attacks. 
Authority to Use Military Force in Libya

25

The March 21 report also identified the risks to regional and international peace and security that, in the President’s judgment, had justified 

military intervention:

Qadhafi’s continued attacks and threats against civilians and civilian 

populated areas are of grave concern to neighboring Arab nations 

and, as expressly stated in U.N. Security Council Resolution 1973, 

constitute a threat to the region and to international peace and security. His illegitimate use of force not only is causing the deaths of substantial numbers of civilians among his own people, but also is forcing many others to flee to neighboring countries, thereby 

destabilizing the peace and security of the region. Left unaddressed, 

the growing instability in Libya could ignite wider instability in the 

Middle East, with dangerous consequences to the national security 

interests of the United States. Qadhafi’s defiance of the Arab 

League, as well as the broader international community . . . represents a lawless challenge to the authority of the Security Council and 

its efforts to preserve stability in the region. Qadhafi has forfeited 

his responsibility to protect his own citizens and created a serious 

need for immediate humanitarian assistance and protection, with any 

delay only putting more civilians at risk.

Id. Emphasizing that “[t]he United States has not deployed ground forces 

into Libya,” the President explained that “United States forces are conducting a limited and well-defined mission in support of international 

efforts to protect civilians and prevent a humanitarian disaster” and thus 

had targeted only “the Qadhafi regime’s air defense systems, command 

and control structures, and other capabilities of Qadhafi’s armed forces 

used to attack civilians and civilian populated areas.” Id. The President 

also indicated that “[w]e will seek a rapid, but responsible, transition of 

operations to coalition, regional, or international organizations that are 

postured to continue activities as may be necessary to realize the objectives of U.N. Security Council Resolutions 1970 and 1973.” Id. As authority for the military operations in Libya, President Obama invoked his 

“constitutional authority to conduct U.S. foreign relations” and his authority “as Commander in Chief and Chief Executive.” Id.

Before the initiation of military operations in Libya, White House and 

other executive branch officials conducted multiple meetings and brief-
35 Op. O.L.C. 20 (2011)

26

ings on Libya with members of Congress and testified on the Administration’s policy at congressional hearings. See Press Release, Office of 

the Press Secretary, Press Gaggle by Press Secretary Jay Carney, 

3/14/2011 (Mar. 24, 2011), http://www.whitehouse.gov/the-press-office/

2011/03/24/press-gaggle-press-secretary-jay-carney-3242011 (last visited ca. Apr. 2011). President Obama invited Republican and Democratic 

leaders of Congress to the White House for consultation on March 18, 

2011 before launching United States military operations, see id., and 

personally briefed members of Congress on the ongoing operations 

on March 25, 2011. Press Release, Office of the Press Secretary, 

Readout of the President’s Meeting with Members of Congress on Libya 

(Mar. 25, 2011), http://www.whitehouse.gov/the-press-office/2011/03/

25/readout-presidents-meeting-members-congress-libya (last visited ca.

Apr. 2011). Senior executive branch officials are continuing to brief 

Senators and members of Congress on U.S. operations and events in 

Libya as they develop.

On March 28, 2011, President Obama addressed the nation regarding 

the situation in Libya. The President stated that the coalition had succeeded in averting a massacre in Libya and that the United States was now 

transferring “the lead in enforcing the no-fly zone and protecting civilians 

on the ground . . . to our allies and partners.” March 28, 2011 Address. In 

future coalition operations in Libya, the President continued, “the United 

States will play a supporting role—including intelligence, logistical 

support, search and rescue assistance, and capabilities to jam regime 

communications.” Id. The President also reiterated the national interests 

supporting military action by the United States. “[G]iven the costs and 

risks of intervention,” he explained, “we must always measure our interests against the need for action.” Id. But, “[i]n this particular country—

Libya—at this particular moment, we were faced with the prospect of 

violence on a horrific scale,” and “[w]e had a unique ability to stop that 

violence.” Id. Failure to prevent a slaughter would have disregarded 

America’s “important strategic interest in preventing Qaddafi from overrunning those who oppose him”:

A massacre would have driven thousands of additional refugees 

across Libya’s borders, putting enormous strains on the peaceful—

yet fragile—transitions in Egypt and Tunisia. The democratic impulses that are dawning across the region would be eclipsed by the 
Authority to Use Military Force in Libya

27

darkest form of dictatorship, as repressive leaders concluded that violence is the best strategy to cling to power. The writ of the United 

Nations Security Council would have been shown to be little more 

than empty words, crippling that institution’s future credibility to 

uphold global peace and security. So while I will never minimize the 

costs involved in military action, I am convinced that a failure to act 

in Libya would have carried a far greater price for America.

Id. As of March 31, 2011, the United States had transferred responsibility 

for all ongoing coalition military operations in Libya to the North Atlantic 

Treaty Alliance (“NATO”).

II.

The President explained in his March 21, 2011 report to Congress that 

the use of military force in Libya serves important U.S. interests in preventing instability in the Middle East and preserving the credibility and 

effectiveness of the United Nations Security Council. The President also 

stated that he intended the anticipated United States military operations in 

Libya to be limited in nature, scope, and duration. The goal of action by 

the United States was to “set the stage” for further action by coalition 

partners in implementing UNSC Resolution 1973, particularly through 

destruction of Libyan military assets that could either threaten coalition 

aircraft policing the UNSC-declared no-fly zone or engage in attacks on 

civilians and civilian-populated areas. In addition, no U.S. ground forces 

would be deployed, except possibly for any search and rescue missions, 

and the risk of substantial casualties for U.S. forces would be low. As we 

advised you prior to the commencement of military operations, we believe 

that, under these circumstances, the President had constitutional authority, 

as Commander in Chief and Chief Executive and pursuant to his foreign 

affairs powers, to direct such limited military operations abroad, even 

without prior specific congressional approval.

A.

Earlier opinions of this Office and other historical precedents establish 

the framework for our analysis. As we explained in 1992, Attorneys 

General and this Office “have concluded that the President has the power 

to commit United States troops abroad,” as well as to “take military 
35 Op. O.L.C. 20 (2011)

28

action,” “for the purpose of protecting important national interests,” even 

without specific prior authorization from Congress. Authority to Use 

United States Military Forces in Somalia, 16 Op. O.L.C. 6, 9 (1992) 

(“Military Forces in Somalia”). This independent authority of the President, which exists at least insofar as Congress has not specifically restricted it, see Deployment of United States Armed Forces Into Haiti, 18 

Op. O.L.C. 173, 176 n.4, 178 (1994) (“Haiti Deployment I”), derives 

from the President’s “unique responsibility,” as Commander in Chief and 

Chief Executive, for “foreign and military affairs,” as well as national 

security. Sale v. Haitian Centers Council, Inc., 509 U.S. 155, 188 (1993); 

U.S. Const. art. II, § 1, cl. 1; id. § 2, cl. 2.

The Constitution, to be sure, divides authority over the military between the President and Congress, assigning to Congress the authority to 

“declare War,” “raise and support Armies,” and “provide and maintain a 

Navy,” as well as general authority over the appropriations on which any 

military operation necessarily depends. U.S. Const. art. I, § 8, cls. 1, 11–

14. Yet, under “the historical gloss on the ‘executive Power’ vested in 

Article II of the Constitution,” the President bears the “‘vast share of 

responsibility for the conduct of our foreign relations,’” Am. Ins. Ass’n v. 

Garamendi, 539 U.S. 396, 414 (2003) (quoting Youngstown Sheet & Tube 

Co. v. Sawyer, 343 U.S. 579, 610–11 (1952) (Frankfurter, J., concurring)), 

and accordingly holds “independent authority ‘in the areas of foreign 

policy and national security.’” Id. at 429 (quoting Haig v. Agee, 453 U.S. 

280, 291 (1981)); see also, e.g., Youngstown Sheet & Tube Co., 343 U.S. 

at 635–36 n.2 (Jackson, J., concurring) (noting President’s constitutional 

power to “act in external affairs without congressional authority”). Moreover, the President as Commander in Chief “superintend[s] the military,” 

Loving v. United States, 517 U.S. 748, 772 (1996), and “is authorized to 

direct the movements of the naval and military forces placed by law at his 

command.” Fleming v. Page, 50 U.S. (9 How.) 603, 615 (1850); see also

Placing of United States Armed Forces Under United Nations Operational or Tactical Control, 20 Op. O.L.C. 182, 184 (1996). The President also 

holds “the implicit advantage . . . over the legislature under our constitutional scheme in situations calling for immediate action,” given that 

imminent national security threats and rapidly evolving military and 

diplomatic circumstances may require a swift response by the United 

States without the opportunity for congressional deliberation and action. 
Authority to Use Military Force in Libya

29

Presidential Power to Use the Armed Forces Abroad Without Statutory 

Authorization, 4A Op. O.L.C. 185, 187 (1980) (“Presidential Power”); 

see also Haig, 453 U.S. at 292 (noting “‘the changeable and explosive 

nature of contemporary international relations, and the fact that the Executive is immediately privy to information which cannot be swiftly 

presented to, evaluated by, and acted upon by the legislature’”) (quoting 

Zemel v. Rusk, 381 U.S. 1, 17 (1965). Accordingly, as Attorney General 

(later Justice) Robert Jackson observed over half a century ago, “the 

President’s authority has long been recognized as extending to the dispatch of armed forces outside of the United States, either on missions of 

goodwill or rescue, or for the purpose of protecting American lives or 

property or American interests.” Training of British Flying Students in the 

United States, 40 Op. Att’y Gen. 58, 62 (1941).

This understanding of the President’s constitutional authority reflects 

not only the express assignment of powers and responsibilities to the 

President and Congress in the Constitution, but also, as noted, the “historical gloss” placed on the Constitution by two centuries of practice. Garamendi, 539 U.S. at 414. “Our history,” this Office observed in 1980, “is 

replete with instances of presidential uses of military force abroad in the 

absence of prior congressional approval.” Presidential Power, 4A Op. 

O.L.C. at 187; see generally Richard F. Grimmett, Cong. Research Serv., 

R41677, Instances of Use of United States Armed Forces Abroad, 1798–

2010 (2011) (“Grimmet”). Since then, instances of such presidential initiative have only multiplied, with Presidents ordering, to give just a few 

examples, bombing in Libya (1986), an intervention in Panama (1989), 

troop deployments to Somalia (1992), Bosnia (1995), and Haiti (twice, 

1994 and 2004), air patrols and airstrikes in Bosnia (1993–1995), and a 

bombing campaign in Yugoslavia (1999), without specific prior authorizing legislation. See Grimmett at 13–31. This historical practice is an 

important indication of constitutional meaning, because it reflects the two 

political branches’ practical understanding, developed since the founding 

of the Republic, of their respective roles and responsibilities with respect 

to national defense, and because “[m]atters intimately related to foreign 

policy and national security are rarely proper subjects for judicial intervention.” Haig, 453 U.S. at 292. In this context, the “pattern of executive 

conduct, made under claim of right, extended over many decades and 

engaged in by Presidents of both parties, ‘evidences the existence of 
35 Op. O.L.C. 20 (2011)

30

broad constitutional power.’” Haiti Deployment I, 18 Op. O.L.C. at 178 

(quoting Presidential Power, 4A Op. O.L.C. at 187); see also Proposed 

Deployment of United States Armed Forces into Bosnia, 19 Op. O.L.C. 

327, 330–31 (1995) (“Proposed Bosnia Deployment”) (noting that “[t]he 

scope and limits” of Congress’s power to declare war “are not well defined by constitutional text, case law, or statute,” but the relationship 

between that power and the President’s authority as Commander in Chief 

and Chief Executive has been instead “clarified by 200 years of practice”).

Indeed, Congress itself has implicitly recognized this presidential authority. The War Powers Resolution (“WPR”), 50 U.S.C. §§ 1541–1548 

(2006), a statute Congress described as intended “to fulfill the intent of 

the framers of the Constitution of the United States,” id. § 1541(a), provides that, in the absence of a declaration of war, the President must 

report to Congress within 48 hours of taking certain actions, including 

introduction of U.S. forces “into hostilities or into situations where imminent involvement in hostilities is clearly indicated by the circumstances.” 

Id. § 1543(a). The Resolution further provides that the President generally 

must terminate such use of force within 60 days (or 90 days for military 

necessity) unless Congress extends this deadline, declares war, or “enact[s] a specific authorization.” Id. § 1544(b). As this Office has explained, although the WPR does not itself provide affirmative statutory 

authority for military operations, see id. § 1547(d)(2), the Resolution’s 

“structure . . . recognizes and presupposes the existence of unilateral 

presidential authority to deploy armed forces” into hostilities or circumstances presenting an imminent risk of hostilities. Haiti Deployment I, 

18 Op. O.L.C. at 175; see also Proposed Bosnia Deployment, 19 Op. 

O.L.C. at 334. That structure—requiring a report within 48 hours after the 

start of hostilities and their termination within 60 days after that—“makes 

sense only if the President may introduce troops into hostilities or potential hostilities without prior authorization by the Congress.” Haiti Deployment I, 18 Op. O.L.C. at 175–76; see also Proposed Bosnia Deployment, 19 Op. O.L.C. at 334–35.1

 1 A policy statement in the WPR states that “[t]he constitutional powers of the President as Commander-in-Chief to introduce United States Armed Forces into hostilities, or 

into situations where imminent involvement in hostilities is clearly indicated by the 

circumstances, are exercised only pursuant to (1) a declaration of war, (2) specific statuto-
Authority to Use Military Force in Libya

31

We have acknowledged one possible constitutionally based limit on 

this presidential authority to employ military force in defense of important

national interests—a planned military engagement that constitutes a “war” 

within the meaning of the Declaration of War Clause may require prior 

congressional authorization. See Proposed Bosnia Deployment, 19 Op. 

O.L.C. at 331; Haiti Deployment I, 18 Op. O.L.C. at 177. But the historical practice of presidential military action without congressional approval 

precludes any suggestion that Congress’s authority to declare war covers 

every military engagement, however limited, that the President initiates. 

In our view, determining whether a particular planned engagement constitutes a “war” for constitutional purposes instead requires a fact-specific 

assessment of the “anticipated nature, scope, and duration” of the planned 

military operations. Haiti Deployment I, 18 Op. O.L.C. at 179. This standard generally will be satisfied only by prolonged and substantial military 

engagements, typically involving exposure of U.S. military personnel to 

significant risk over a substantial period. Again, Congress’s own key 

enactment on the subject reflects this understanding. By allowing United 

States involvement in hostilities to continue for 60 or 90 days, Congress 

signaled in the WPR that it considers congressional authorization most 

critical for “major, prolonged conflicts such as the wars in Vietnam and 

Korea,” not more limited engagements. Id. at 176.

Applying this fact-specific analysis, we concluded in 1994 that a 

planned deployment of up to 20,000 United States troops to Haiti to oust 

military leaders and reinstall Haiti’s legitimate government was not a 

“war” requiring advance congressional approval. Id. at 174 n.1, 178–79 &

 

ry authorization, or (3) a national emergency created by attack upon the United States, its 

territories or possessions, or its armed forces.” 50 U.S.C. § 1541(c). But this policy 

statement “is not to be viewed as limiting presidential action in any substantive manner.” 

Presidential Power, 4A Op. O.L.C. at 190. The conference committee report accompanying the WPR made clear that “[s]ubsequent sections of the [Resolution] are not dependent 

upon the language of” the policy statement. H.R. Rep. No. 93-547, at 8 (1973). Moreover, 

in a later, operative provision, the Resolution makes clear that nothing in it “is intended to 

alter the constitutional authority . . . of the President.” 50 U.S.C. § 1547(d). As demonstrated by U.S. military interventions in Somalia, Haiti, Bosnia, and Kosovo, among many 

other examples, “the President’s power to deploy armed forces into situations of actual 

or indicated hostilities is not restricted to the three categories specifically marked out by 

the Resolution.” Proposed Bosnia Deployment, 19 Op. O.LC. at 335; see also Haiti

Deployment I, 18 Op. O.L.C. at 176 & n.3.
35 Op. O.L.C. 20 (2011)

32

n.10; see also Address to the Nation on Haiti, 30 Weekly Comp. Pres. 

Doc. 1799 (Sept. 18, 1994); Maureen Taft-Morales & Clare Ribando 

Seelke, Cong. Research Serv., RL32294, Haiti: Developments and U.S. 

Policy Since 1991 and Current Congressional Concerns 4 (2008). “In 

deciding whether prior Congressional authorization for the Haitian deployment was constitutionally necessary,” we observed, “the President 

was entitled to take into account the anticipated nature, scope, and duration of the planned deployment, and in particular the limited antecedent 

risk that United States forces would encounter significant armed resistance or suffer or inflict substantial casualties as a result of the deployment.” Haiti Deployment I, 18 Op. O.L.C. at 179. Similarly, a year 

later we concluded that a proposed deployment of approximately 20,000 

ground troops to enforce a peace agreement in Bosnia and Herzegovina 

also was not a “war,” even though this deployment involved some “risk 

that the United States [would] incur (and inflict) casualties.” Proposed 

Bosnia Deployment, 19 Op. O.L.C. at 333. For more than two years preceding this deployment, the United States had undertaken air operations 

over Bosnia to enforce a UNSC-declared “no-fly zone,” protect United 

Nations peacekeeping forces, and secure “safe areas” for civilians, including one two-week operation in which NATO attacked hundreds of targets 

and the United States alone flew over 2300 sorties—all based on the 

President’s “constitutional authority to conduct the foreign relations of the 

United States and as Commander in Chief and Chief Executive,” without 

a declaration of war or other specific prior approval from Congress. Letter 

to Congressional Leaders Reporting on the Deployment of United States 

Aircraft to Bosnia-Herzegovina (Sept. 1, 1995), 2 Pub. Papers of Pres. 

William J. Clinton 1279, 1280 (1995); see also, e.g., Letter to Congressional Leaders on Bosnia, 30 Weekly Comp. Pres. Doc. 2431, 2431 (Nov. 

22, 1994); Letter to Congressional Leaders on Bosnia-Herzegovina, 30 

Weekly Comp. Pres. Doc. 1699, 1700 (Aug. 22, 1994); Letter to Congressional Leaders on Protection of United Nations Personnel in BosniaHerzegovina, 30 Weekly Comp. Pres. Doc. 793, 793 (Apr. 12, 1994); 

Letter to Congressional Leaders Reporting on NATO Action in Bosnia, 30 

Weekly Comp. Pres. Doc. 406, 406 (Mar. 1, 1994); Letter to Congressional Leaders on the Conflict in the Former Yugoslavia, 30 Weekly 

Comp. Pres. Doc. 324, 325 (Feb. 17, 1994); Letter to Congressional 

Leaders Reporting on the No-Fly Zone Over Bosnia, 29 Weekly Comp. 
Authority to Use Military Force in Libya

33

Pres. Doc. 586, 586 (Apr. 13, 1993); Proposed Bosnia Deployment, 19 

Op. O.L.C. at 328–29; Deliberate Force: A Case Study in Effective Air 

Campaigning 334, 341–44 (Col. Robert C. Owen ed., 2000), http://purl.

access.gpo.gov/GPO/LPS20446 (last visited ca. Apr. 2011). This Office 

acknowledged that “deployment of 20,000 troops on the ground is an 

essentially different, and more problematic, type of intervention,” than 

air or naval operations because of the increased risk of United States 

casualties and the far greater difficulty of withdrawing United States 

ground forces. But we nonetheless concluded that the anticipated risks 

were not sufficient to make the deployment a “‘war’ in any sense of the 

word.” Proposed Bosnia Deployment, 19 Op. O.L.C. at 333–34 (emphasis 

in original).

B.

Under the framework of these precedents, the President’s legal authority to direct military force in Libya turns on two questions: first, whether 

United States operations in Libya would serve sufficiently important 

national interests to permit the President’s action as Commander in Chief 

and Chief Executive and pursuant to his authority to conduct U.S. foreign 

relations; and second, whether the military operations that the President 

anticipated ordering would be sufficiently extensive in “nature, scope, and 

duration” to constitute a “war” requiring prior specific congressional 

approval under the Declaration of War Clause.

In prior opinions, this Office has identified a variety of national interests that, alone or in combination, may justify use of military force by the 

President. In 2004, for example, we found adequate legal authority for the 

deployment of U.S. forces to Haiti based on national interests in protecting the lives and property of Americans in the country, preserving “regional stability,” and maintaining the credibility of United Nations Security Council mandates. Deployment of United States Armed Forces to Haiti, 

28 Op. O.L.C. 30, 32–33 (2004) (“Haiti Deployment II”). In 1995, we 

similarly concluded that the President’s authority to deploy approximately 

20,000 ground troops to Bosnia, for purposes of enforcing a peace agreement ending the civil war there, rested on national interests in completing 

a “pattern of inter-allied cooperation and assistance” established by prior 

U.S. participation in NATO air and naval support for peacekeeping efforts, “preserving peace in the region and forestalling the threat of a wider 
35 Op. O.L.C. 20 (2011)

34

conflict,” and maintaining the credibility of the UNSC. Proposed Bosnia 

Deployment, 19 Op. O.L.C. at 332–33. And in 1992, we explained the 

President’s authority to deploy troops in Somalia in terms of national 

interests in providing security for American civilians and military personnel involved in UNSC-supported humanitarian relief efforts and (once 

again) enforcing UNSC mandates. Military Forces in Somalia, 16 Op. 

O.L.C. at 10–12.2

In our view, the combination of at least two national interests that the 

President reasonably determined were at stake here—preserving regional 

stability and supporting the UNSC’s credibility and effectiveness—

provided a sufficient basis for the President’s exercise of his constitutional authority to order the use of military force.3 First, the United States has 

a strong national security and foreign policy interest in security and stability in the Middle East that was threatened by Qadhafi’s actions in Libya. 

As noted, we recognized similar regional stability interests as justifications for presidential military actions in Haiti and Bosnia. With respect to 

Haiti, we found “an obvious interest in maintaining peace and stability,” 

“[g]iven the proximity of Haiti to the United States,” and particularly 

considering that “past instances of unrest in Haiti have led to the mass 

emigration of refugees attempting to reach the United States.” Haiti 

Deployment II, 28 Op. O.L.C. at 32–33. In the case of Bosnia, we noted 

(quoting prior statements by President Clinton justifying military action) 

the longstanding commitment of the United States to the “‘principle that 

the security and stability of Europe is of fundamental interest to the United States,’” and we identified, as justification for the military action, the 

 

2 As these examples make clear, defense of the United States to repel a direct and immediate military attack is by no means the only basis on which the President may use 

military force without congressional authorization. Accordingly, the absence of an 

immediate self-defense interest does not mean that the President lacked authority for the 

military operations in Libya.

3 Although President Obama has expressed opposition to Qadhafi’s continued leadership of Libya, we understand that regime change is not an objective of the coalition’s 

military operations. See March 28, 2011 Address (“Of course, there is no question that 

Libya—and the world—would be better off with Qaddafi out of power. I . . . will actively 

pursue [that goal] through non-military means. But broadening our military mission to 

include regime change would be a mistake.”). We therefore do not consider any national 

interests relating to regime change in assessing the President’s legal authority to order 

military operations in Libya.
Authority to Use Military Force in Libya

35

President’s determination that “[i]f the war in the former Yugoslavia 

resumes, ‘there is a very real risk that it could spread beyond Bosnia, and 

involve Europe’s new democracies as well as our NATO allies.’” Proposed Bosnia Deployment, 19 Op. O.L.C. at 333. In addition, in another 

important precedent, President Clinton justified extensive airstrikes in the 

Federal Republic of Yugoslavia (“FRY”) in 1999—military action later 

ratified by Congress but initially conducted without specific authorization, 

see Authorization for Continuing Hostilities in Kosovo, 24 Op. O.L.C. 327 

(2000)—based on concerns about the threat to regional security created by 

that government’s repressive treatment of the ethnic Albanian population 

in Kosovo. “The FRY government’s violence,” President Clinton explained, “creates a conflict with no natural boundaries, pushing refugees 

across borders and potentially drawing in neighboring countries. The 

Kosovo region is a tinderbox that could ignite a wider European war with

dangerous consequences to the United States.” Letter to Congressional 

Leaders Reporting on Airstrikes Against Serbian Targets in the Federal 

Republic of Yugoslavia (Serbia and Montenegro), 35 Weekly Comp. Pres. 

Doc. 527, 527 (Mar. 26, 1999).

As his statements make clear, President Obama determined in this case that 

the Libyan government’s actions posed similar risks to regional peace and 

security. Much as violence in Bosnia and Kosovo in the 1990s risked creating 

large refugee movements, destabilizing neighboring countries, and inviting 

wider conflict, here the Libyan government’s “illegitimate use of force . . . 

[was] forcing many [civilians] to flee to neighboring countries, thereby destabilizing the peace and security of the region.” March 21, 2011 Report to 

Congress. “Left unaddressed,” the President noted in his report to Congress, 

“the growing instability in Libya could ignite wider instability in the Middle 

East, with dangerous consequences to the national security interests of the 

United States.” Id. Without outside intervention, Libya’s civilian population 

faced a “humanitarian catastrophe,” id.; as the President put it on another 

occasion, “innocent people” in Libya were “being brutalized” and Qadhafi 

“threaten[ed] a bloodbath that could destabilize an entire region.” Press Release, Office of the Press Secretary, The White House, Weekly Address: 

President Obama Says the Mission in Libya is Succeeding (Mar. 26, 2011),

http://www.whitehouse.gov/the-press-office/2011/03/26/weekly-addresspresident-obama-says-mission-libya-succeeding (last visited ca. Apr. 2011). 

The risk of regional destabilization in this case was also recognized by the 
35 Op. O.L.C. 20 (2011)

36

UNSC, which determined in Resolution 1973 that the “situation” in Libya 

“constitute[d] a threat to international peace and security.” S.C. Res. 1973. As 

this Office has previously observed, “[t]he President is entitled to rely on” 

such UNSC findings “in making his determination that the interests of the 

United States justify providing the military assistance that [the UNSC resolution] calls for.” Military Forces in Somalia, 16 Op. O.L.C. at 12.4

Qadhafi’s actions not only endangered regional stability by increasing 

refugee flows and creating a humanitarian crisis, but, if unchecked, also 

could have encouraged the repression of other democratic uprisings that 

were part of a larger movement in the Middle East, thereby further undermining United States foreign policy goals in the region. Against the 

background of widespread popular unrest in the region, events in Libya 

formed “just one more chapter in the change that is unfolding across the 

Middle East and North Africa.” March 18, 2011 Remarks. Qadhafi’s 

campaign of violence against his own country’s citizens thus might have 

set an example for others in the region, causing “[t]he democratic impulses that are dawning across the region [to] be eclipsed by the darkest 

form of dictatorship, as repressive leaders concluded that violence is the 

best strategy to cling to power.” March 28, 2011 Address. At a minimum, 

a massacre in Libya could have imperiled transitions to democratic 

government underway in neighboring Egypt and Tunisia by driving 

“thousands of additional refugees across Libya’s borders.” Id. Based on 

these factors, we believe the President could reasonably find a significant 

national security interest in preventing Libyan instability from spreading 

elsewhere in this critical region. 

The second important national interest implicated here, which reinforces the first, is the longstanding U.S. commitment to maintaining the 

credibility of the United Nations Security Council and the effectiveness

of its actions to promote international peace and security. Since at least 

the Korean War, the United States government has recognized that 

“‘[t]he continued existence of the United Nations as an effective interna-

 4 We note, however, that, at least for purposes of domestic law, a Security Council 

resolution is “not required as a precondition for Presidential action.” Military Forces in 

Somalia, 16 Op. O.L.C. at 7. Rather, as we explained in 2004, “in exercising his authority 

as Commander in Chief and Chief Executive, the President [may] choose to take” the 

UNSC resolution into account “in evaluating the foreign policy and national security 

interests of the United States that are at stake.” Haiti Deployment II, 28 Op. O.L.C. at 33. 
Authority to Use Military Force in Libya

37

tional organization is a paramount United States interest.’” Military 

Forces in Somalia, 16 Op. O.L.C. at 11 (quoting Authority of the President to Repel the Attack in Korea, 23 Dep’t of State Bull. 173, 177 

(1950)). Accordingly, although of course the President is not required to 

direct the use of military force simply because the UNSC has authorized 

it, this Office has recognized that “‘maintaining the credibility of United 

Nations Security Council decisions, protecting the security of United 

Nations and related relief efforts, and ensuring the effectiveness of United Nations peacekeeping operations can be considered a vital national 

interest’” on which the President may rely in determining that U.S. 

interests justify the use of military force. Proposed Bosnia Deployment, 

19 Op. O.L.C. at 333 (quoting Military Forces in Somalia, 16 Op. O.L.C. 

at 11). Here, the UNSC’s credibility and effectiveness as an instrument 

of global peace and stability were at stake in Libya once the UNSC took 

action to impose a no-fly zone and ensure the safety of civilians—

particularly after Qadhafi’s forces ignored the UNSC’s call for a cease 

fire and for the cessation of attacks on civilians. As President Obama 

noted, without military action to stop Qadhafi’s repression, “[t]he writ of 

the United Nations Security Council would have been shown to be little 

more than empty words, crippling that institution’s future credibility to 

uphold global peace and security.” March 28, 2011 Address; see also 

March 21, 2011 Report to Congress (“Qadhafi’s defiance of the Arab 

League, as well as the broader international community . . . represents a 

lawless challenge to the authority of the Security Council and its efforts 

to preserve stability in the region.”). We think the President could legitimately find that military action by the United States to assist the international coalition in giving effect to UNSC Resolution 1973 was needed to 

secure “a substantial national foreign policy objective.” Military Forces 

in Somalia, 16 Op. O.L.C. at 12.

We conclude, therefore, that the use of military force in Libya was supported by sufficiently important national interests to fall within the President’s constitutional power. At the same time, turning to the second 

element of the analysis, we do not believe that anticipated United States 

operations in Libya amounted to a “war” in the constitutional sense necessitating congressional approval under the Declaration of War Clause. This 

inquiry, as noted, is highly fact-specific and turns on no single factor. See 

Proposed Bosnia Deployment, 19 Op. O.L.C. at 334 (reaching conclusion 
35 Op. O.L.C. 20 (2011)

38

based on specific “circumstances”); Haiti Deployment I, 18 Op. O.L.C. at 

178 (same). Here, considering all the relevant circumstances, we believe 

applicable historical precedents demonstrate that the limited military 

operations the President anticipated directing were not a “war” for constitutional purposes.

As in the case of the no-fly zone patrols and periodic airstrikes in Bosnia before the deployment of ground troops in 1995 and the NATO bombing campaign in connection with the Kosovo conflict in 1999—two military campaigns initiated without a prior declaration of war or other 

specific congressional authorization—President Obama determined that 

the use of force in Libya by the United States would be limited to airstrikes and associated support missions; the President made clear that 

“[t]he United States is not going to deploy ground troops in Libya.” 

March 18, 2011 Remarks. The planned operations thus avoided the difficulties of withdrawal and risks of escalation that may attend commitment 

of ground forces—two factors that this Office has identified as “arguably” 

indicating “a greater need for approval [from Congress] at the outset,” to 

avoid creating a situation in which “Congress may be confronted with 

circumstances in which the exercise of its power to declare war is effectively foreclosed.” Proposed Bosnia Deployment, 19 Op. O.L.C. at 333. 

Furthermore, also as in prior operations conducted without a declaration 

of war or other specific authorizing legislation, the anticipated operations 

here served a “limited mission” and did not “aim at the conquest or occupation of territory.” Id. at 332. President Obama directed United States 

forces to “conduct[] a limited and well-defined mission in support of 

international efforts to protect civilians and prevent a humanitarian disaster”; American airstrikes accordingly were to be “limited in their nature, 

duration, and scope.” March 21, 2011 Report to Congress. As the President explained, “we are not going to use force to go beyond [this] welldefined goal.” March 18, 2011 Remarks. And although it might not be 

true here that “the risk of sustained military conflict was negligible,” the 

anticipated operations also did not involve a “preparatory bombardment” 

in anticipation of a ground invasion—a form of military operation we 

distinguished from the deployment (without preparatory bombing) of 

20,000 U.S. troops to Haiti in concluding that the latter operation did not 

require advance congressional approval. Haiti Deployment I, 18 Op. 

O.L.C. at 176, 179. Considering the historical practice of even intensive 
Authority to Use Military Force in Libya

39

military action—such as the 17-day-long 1995 campaign of NATO airstrikes in Bosnia and some two months of bombing in Yugoslavia in 

1999—without specific prior congressional approval, as well as the limited means, objectives, and intended duration of the anticipated operations 

in Libya, we do not think the “anticipated nature, scope, and duration” of 

the use of force by the United States in Libya rose to the level of a “war” 

in the constitutional sense, requiring the President to seek a declaration of 

war or other prior authorization from Congress.

Accordingly, we conclude that President Obama could rely on his constitutional power to safeguard the national interest by directing the anticipated military operations in Libya—which were limited in their nature, 

scope, and duration—without prior congressional authorization.

CAROLINE D. KRASS

Principal Deputy Assistant Attorney General

Office of Legal Counsel