War Powers

This page discusses the distribution and scope of the war powers --- including the powers to initiate, conduct, and end hostilities --- among the branches of the United States government. It includes a chronological list of significant military engagements by the United States and links to U.S. legal documents and judicial decisions about these events.

Although the issues of covert action and domestic restrictions on civil liberties during war (e.g., detention or internment) are related, they are discussed in other pages.

Constitutional Sources of War Powers

The Constitution divides war powers between the legislative and executive branches. Article I of the the Constitution gives Congress the power:

"To define and punish Piracies and Felonies committed on the high Seas, and Offences against the Law of Nations." Art. I, § 8, cl. 10.
"To declare War, grant Letters of Marque and Reprisal, and make Rules concerning Captures on Land and Water." Art. I, § 8, cl. 11.
"To raise and support Armies, but no Appropriation of Money to that Use shall be for a longer Term than two Years." Art. I, § 8, cl. 12.
"To provide and maintain a Navy." Art. I, § 8, cl. 13.
"To make Rules for the Government and Regulation of the land and naval Forces." Art. I, § 8, cl. 14.
"To provide for calling forth the Militia to execute the Laws of the Union, suppress Insurrections and repel Invasions." Art. I, § 8, cl. 15.
"To provide for organizing, arming, and disciplining, the Militia, and for governing such Part of them as may be employed in the Service of the United States, reserving to the States respectively, the Appointment of the Officers, and the Authority of training the Militia according to the discipline prescribed by Congress." Art. I, § 8, cl. 16.
"To make all Laws which shall be necessary and proper for carrying into Execution the foregoing Powers, and all other Powers vested by this Constitution in the Government of the United States, or in any Department or Officer thereof." Art. I, § 8, cl. 18.

The executive's war powers stem primarily from three constitutional provisions:

Vesting clause, Art. II, § 1, cl. 1: "The executive Power shall be vested in a President of the United States of America."
Commander-in-Chief clause, Art. II, § 2, cl. 1: "The President shall be Commander in Chief of the Army and Navy of the United States, and of the Militia of the several States, when called into the actual Service of the United States . . . ."
Take Care clause, Art. II, § 3: The President "shall take Care that the Laws be faithfully executed . . . ."

The Constitution extends judicial power "to all Cases, in Law and Equity, arising under this Constitution, the Laws of the United States, and Treaties made, or which shall be made, under their Authority . . . ." Art. III, § 2, cl. 1.

The judiciary has jurisdiction over the many federal law issues that can arise in war, and has often ruled on matters related to war. However, the courts have generally declined to rule on which branch has the authority to initiate war, and relatedly, when war is lawful. Examples of such reticence include:

Schlesinger v. Holtzman, 414 U.S. 1321 (1973) (dismissing challenge to bombing in Cambodia on political question grounds)
Campbell v. Clinton, 203 F.3d 19 (D.C. Cir. 2000) (dismissing challenge to Kosovo bombing campaign on standing grounds)
Ange v. Bush, 752 F. Supp. 509 (D.D.C. 1990) (dismissing challenge to Gulf War on political question, equitable discretion, and ripeness grounds)
Lowry v. Reagan, 676 F. Supp. 333 (D.D.C. 1987) (dismissing challenge to reflagging operation in the Persian Gulf on equitable discretion and political question grounds)
Sanchez-Espinoza v. Reagan, 568 F. Supp. 596 (D.D.C. 1983) (dismissing challenge to covert assistance to Nicaraguan Contras on political question grounds)
Crockett v. Reagan, 558 F. Supp. 893 (D.D.C. 1982) (dismissing challenge to military aid to El Salvador on political question grounds)

The Constitution explicitly prohibits the states from engaging in war, at least without congressional authorization:

"No State shall enter into any Treaty, Alliance, or Confederation; grant Letters of Marque and Reprisal; coin Money; emit Bills of Credit; make any Thing but gold and silver Coin a Tender in Payment of Debts; pass any Bill of Attainder, ex post facto Law, or Law impairing the Obligation of Contracts, or grant any Title of Nobility." Art. I, § 10, cl. 1.
"No State shall, without the Consent of Congress, lay any Duty of Tonnage, keep Troops, or Ships of War in time of Peace, enter into any Agreement or Compact with another state, or with a foreign Power, or engage in War, unless actually invaded, or in such imminent Danger as will not admit of delay." Art. I, § 10, cl. 3.

Military Interventions by the United States and Legal Documents About Military Action

This list focuses on significant uses of force by the United States. All dates are approximate. The list includes the five declared wars in which the United States has so far fought: the War of 1812, the Mexican-American War, the Spanish-American War, World War I, and World War II. It also includes uses of military force in many other situations, both authorized by Congress and unauthorized.

Additional events or documents may be added by contributors to the Lawfare Wiki Document Library.

18th Century

The Quasi-War: 1798-1800

Act more effectually to Protect the Commerce and Coasts of the United States (Act of May 28, 1798, ch. 48, 1 Stat. 561)
Act in addition to the act more effectually to protect the Commerce and Coasts of the United States (Act of June 28, 1798, ch. 62, 1 Stat. 574)
Act Further to Protect the Commerce of the United States (Act of July 9, 1798, ch. 68, 1 Stat. 578)
Bas v. Tingy, 4 U.S. (4 Dall.) 37 (1800) (statutory authorization for the Quasi-War)
Little v. Barreme, 6 U.S. (2 Cranch) 170 (1804) (Congress's power to regulate captures during the Quasi-War)

Other 18th Century Statutes and Legal Documents About Military Action

Early Militia Statutes

Act to recognize and adopt to the Constitution of the United States the establishment of the Troops Raised under the Resolves of the United States in Congress Assembled, and for other purposes therein mentioned (Act of Sept. 29, 1789, ch. 25, 1 Stat. 95)
Act for regulating the Military Establishment of the United States (Act of Apr. 30, 1790, ch. 10, 1 Stat. 119)
Act to provide for calling forth the Militia to execute the laws of the Union, suppress insurrections and repel invasions (First Militia Act of 1792) (Act of May 2, 1792, ch. 28, 1 Stat. 264)
Act more effectually to provide for the National Defence by establishing an Uniform Militia throughout the United States (Second Militia Act of 1792) (Act of May 8, 1792, ch. 33, 1 Stat. 271)
Act to provide for calling forth the Militia to execute the laws of the Union, suppress insurrections, and repel invasions; and to repeal the Act now in force for those purposes (Militia Act of 1795, amending the First Militia Act of 1792) (Act of Feb. 28, 1795, ch. 36, 1 Stat. 424)

Native American Relations

Act to regulate Trade and Intercourse with the Indian Tribes, and to preserve Peace on the Frontiers (Act of May 19, 1796, ch. 30, § 5, 1 Stat. 469, 470)
Act to regulate trade and intercourse with the Indian tribes, and to preserve peace on the frontiers (Act of Mar. 3, 1799, ch. 46, § 5, 1 Stat. 743, 745)

19th Century

First Barbary War: 1801-1805

Act for the protection of the Commerce and Seamen of the United States, against the Tripolitan Cruisers (Act of Feb. 6, 1802, ch. 4, 2 Stat. 129)
Act for the more effectual preservation of peace in the ports and harbors of the United States, and in the waters under their jurisdiction (Act of Mar. 3, 1805, ch. 41, § 5, 2 Stat. 339, 341)

Florida: 1811

Act to enable the President of the United States, under certain contingencies, to take possession of the country lying east of the river Perdido, and south of the state of Georgia and the Mississippi territory, and for other purposes (Act of Jan. 15, 1811, 3 Stat. 471)

Amelia Island and East Florida: 1812

War of 1812: 1812-1815

Act authorizing the President of the United States to accept and organize certain Volunteer Military Corps (Act of Feb. 6, 1812, ch. 21, 2 Stat. 676)
Declaring War between the United Kingdom of Great Britain and Ireland and the dependencies thereof, and the United States of America and their territories (Act of June 18, 1812, ch. 102, 2 Stat. 755)
Laying an embargo on all ships and vessels in the ports and harbours of the United States (Embargo Act of 1813) (Act of Dec. 17, 1813, ch. 1, 3 Stat. 88)
Brown v. United States, 12 U.S. (8 Cranch) 110 (1814) (scope of War of 1812 declaration of war)

The Seminole Wars: 1814-1819, 1835-1842, 1855-1858

Act authorizing the President of the United States to accept the service of volunteers, and to raise an additional regiment of dragoons or mounted riflemen (Act of May 23, 1836, ch. 80, 5 Stat. 32)

Second Barbary War: 1815-1816

Act for the protection of commerce of the United States against the Algerine cruisers (Act of Mar. 3, 1815, ch. 90, 3 Stat. 230)

East and West Florida: 1819

Act to authorize the President of the United States to take possession of East and West Florida, and establish a temporary government therein (Act of Mar. 3, 1819, ch. 93, 3 Stat. 523)

Africa: 1820-23

Act in addition to the Acts prohibiting the slave trade (Act of Mar. 3, 1819, ch. 101, 3 Stat. 532)

Cuba: 1822-1825

Mexico: 1844

Mexican-American War: 1846-1848

President James K. Polk's Special Message to Congress on Mexican Relations, May 11, 1846, reprinted in Cong. Globe, 29th Cong., 1st Sess. 783 (1846)
Act Providing for the Prosecution of the existing War between the United States and the Republic of Mexico (Act of May 13, 1846, ch. 16, 9 Stat. 9)
House of Representatives Resolution, Cong. Globe, 30th Cong., 1st Sess. 95 (1848) (condemning the war as "unnecessarily and unconstitutionally begun")

Nicaragua: 1854

Durand v. Hollins, 8 F. Cas. 111 (C.C.S.D.N.Y. 1860) (bombardment of Greytown, Nicaragua)

Paraguay: 1859

Joint Resolution for the Adjustment of Difficulties with the Republic of Paraguay (Joint Resolution 15, June 2, 1858, 35th Cong., 11 Stat. 370)

Civil War: 1861-1865

Presidential Proclamation No. 3 of 1861, Apr. 15, 1861, reprinted in 12 Stat. 1258 (calling forth the militia; convening an extraordinary session of Congress)
Presidential Proclamation No. 4 of 1861, Apr. 19, 1861, reprinted in 12 Stat. 1258 (declaring a blockade of the ports of South Carolina, Georgia, Alabama, Florida, Mississippi, Louisiana, and Texas)
Presidential Proclamation No. 5 of 1861, Apr. 27, 1861, reprinted in 12 Stat. 1259 (extending the blockade to the ports of Virginia and North Carolina)
President Abraham Lincoln's Special Session Message, July 4, 1861 (explaining actions in response to attack on Fort Sumter)
Act to authorize the Employment of Volunteers to aid in enforcing the Laws and protecting Public Property (Act of July 22, 1861, ch. 9, 12 Stat. 268)
Act to provide for the Suppression of Rebellion against and Resistance to the Laws of the United States, and to amend the Act entitled An Act to provide for calling forth the Militia to execute the Laws of the Union, &c., passed February twenty-eight, seventeen hundred and ninety-five (Act of July 29, 1861, ch. 25, 12 Stat. 281)
Act to increase the Pay of the Privates in the Regular Army and in the Volunteers in the Service of the United States, and for other Purposes (Act of Aug. 6, 1861, ch. 63, § 3, 12 Stat. 326, 326) (affirming that "all the acts, proclamations, and orders of the President of the United States after the fourth of March, eighteen hundred and sixty-one, respecting the army and navy of the United States, and calling out or relating to the militia or volunteers from the States, are hereby approved and in all respects legalized and made valid . . . .")
The Prize Cases, 67 U.S. (2 Black) 635 (1863) (concluding that the President had authority to blockade the ports of the rebelling southern states)
Ex parte Milligan, 71 U.S. (4 Wall.) 2 (1866) (concluding that civilian citizens could not constitutionally be tried by military commissions when the federal courts were open and martial law was not in effect)
Presidential Proclamation No. 1 of 1866, Apr. 2, 1866, reprinted in 14 Stat. 811 (declaring the "insurrection . . . at an end" in most southern states)
Presidential Proclamation No. 4 of 1866, Aug. 20, 1866, reprinted in 14 Stat. 814 (declaring the "insurrection . . . at an end" in Texas)
The Protector, 79 U.S. (12 Wall.) 700 (1871) (concluding that presidential proclamations determined the beginning and ending dates of the Civil War, at least "[i]n the absence of more certain criteria")

Mexico: 1873-1896

Spanish-American War: 1898

Declaring that war exists between the United States of America and the Kingdom of Spain (Act of Apr. 25, 1898, ch. 189, 30 Stat. 364)

China: 1900

Other 19th Century Statutes and Legal Documents About Military Action

Militia

Act authorizing the employment of the land and naval forces of the United States, in cases of insurrections (Act of Mar. 3, 1807, ch. 39, 2 Stat. 443)

Native American Relations

Act to provide for an exchange of lands with the Indians residing in any of the states or territories, and for their removal west of the river Mississippi (Removal Act of 1830) (Act of May 28, 1830, ch. 148, 4 Stat. 411)
Act to regulate trade and intercourse with the Indian tribes, and to preserve peace on the frontiers (Indian Intercourse Act of 1834) (Act of June 30, 1834, ch. 161, § 11, 4 Stat. 729, 730)

Piracy

Act to protect the commerce of the United States, and punish the crime of piracy (Act of Mar. 3, 1819, ch. 77, 3 Stat. 510)

Property: Protection of Property and Indemnification for Losses

Joint Resolution for the relief of the Venezuela Steam Transportation Company (Joint Resolution 28, June 7, 1890, 51st Cong., 26 Stat. 674)
Act to provide for the protection of the salmon fisheries of Alaska (Act of Mar. 2, 1889, ch. 415, 25 Stat. 1009)

Slavery

Act to prohibit the importation of Slaves into any port or place within the jurisdiction of the United States, from and after the first day of January, in the year of our Lord one thousand eight hundred and eight (Act of Mar. 2, 1807, ch. 22, § 7, 2 Stat. 426, 428)
Act in addition to the Acts prohibiting the slave trade (Act of Mar. 3, 1819, ch. 101, 3 Stat. 532)

Trade

Act to interdict the commercial intercourse between the United States and Great Britain and France, and their dependencies; and for other purposes (Non-Intercourse Act) (Act of Mar. 1, 1809, ch. 24, 2 Stat. 528)

Use of the Military for Civilian Law Enforcement

Act making appropriations for the support of the Army for the fiscal year ending June thirtieth, eighteen hundred and seventy-nine, and for other purposes (Posse Comitatus Act) (Act of June 18, 1878, ch. 263, § 15, 20 Stat. 145, 152), current version at 18 U.S.C. § 1385, exceptions at 10 U.S.C. §§ 333, 371-372

20th Century

World War I: 1914-1919

Message from President Wilson to Congress, Apr. 2, 1917, in 55 Cong. Rec. 103 (1917)
Declaring that a state of war exists between the Imperial German Government and the Government and the people of the United States and making provision to prosecute the same (Joint Resolution of Apr. 6, 1917, ch. 1, 40 Stat. 1)
Declaring that a state of war exists between the Imperial and Royal Austro-Hungarian Government and the Government and the people of the United States, and making provision to prosecute the same (Joint Resolution of Dec. 7, 1917, ch. 1, 40 Stat. 429)
Hamilton v. Ky. Distilleries & Warehouse Co., 251 U.S. 146 (1919) (interpreting the War-Time Prohibition Act and explaining the scope of Congress's war power)

World War II: 1939-1945

Declaring that a state of war exists between the Imperial Government of Japan and the Government and the people of the United States and making provisions to prosecute the same (Joint Resolution of Dec. 8, 1941, ch. 561, 55 Stat. 795)
Declaring that a state of war exists between the Government of Germany and the Government and the people of the United States and making provision to prosecute the same (Joint Resolution of Dec. 11, 1941, ch. 564, 55 Stat. 796)
Declaring that a state of war exists between the Government of Italy and the Government and the people of the United States and making provision to prosecute the same (Joint Resolution of Dec. 11, 1941, ch. 565, 55 Stat. 797)
Declaring that a state of war exists between the Government of Bulgaria and the Government and the people of the United States and making provisions to prosecute the same (Joint Resolution of June 5, 1942, ch. 323, 56 Stat. 307)
Declaration that a state of war exists between the Government of Hungary and the Government and the people of the United States and making provisions to prosecute the same (Joint Resolution of June 5, 1942, ch. 324, 56 Stat. 307)
Declaring that a state of war exists between the Government of Rumania and the Government and the people of the United States and making provisions to prosecute the same (Joint Resolution of June 5, 1942, ch. 325, 56 Stat. 307)
Ex parte Quirin, 317 U.S. 1 (1942) (concluding that an unlawful enemy combatant captured in the United States during war time and charged with violating the laws of war could constitutionally be tried by a congressionally authorized military commission, even if the combatant was a U.S. citizen)
Order Authorizing the Secretary of War to Prescribe Military Areas, Exec. Order 9066, 7 Fed. Reg. 1407 (Feb. 19, 1942)
Act to provide a penalty for violation of restrictions or orders with respect to persons entering, remaining in, leaving, or committing any act in military areas or zones (Act of Mar. 21, 1942, ch. 191, 56 Stat. 173)
Korematsu v. United States, 323 U.S. 214 (1944) (upholding the constitutionality of Executive Order 9066, pursuant to which the United States excluded Japanese-Americans from the West Coast area, and imposed curfews and/or detention in relocation centers)
Ex parte Endo, 323 U.S. 283 (1944) (concluding that the War Relocation Authority, a civilian agency, lacked power to detain citizens concededly loyal to the United States)
Ludecke v. Watkins, 335 U.S. 160 (1948) (concluding that the President retained power under the Alien Enemy Act to order individuals removed from the country until the political branches declare that war has ended, and stating that "[w]hether and when it would be open to this Court to find that a war though merely formally kept alive had in fact ended" was "a question too fraught with gravity even to be adequately formulated when not compelled")

Korean War: 1950-1953

Youngstown Sheet & Tube Co. v. Sawyer, 343 U.S. 579 (1952) (concluding that the President's executive order directing the Secretary of Commerce to seize steel plants owned by companies involved in labor disputes to prevent interruptions in war-related manufacturing exceeded his authority under the Constitution)

Taiwan: 1950-1955

Joint Resolution Authorizing the President to employ the Armed Forces of the United States for protecting the security of Formosa, the Pescadores and related positions and territories of that area (Joint Resolution of Jan. 29, 1955, ch. 4, 69 Stat. 7)

Middle East: 1958

Joint Resolution to promote peace and stability in the Middle East (Joint Resolution of Mar. 9, 1957, Pub. L. No. 87-5, 71 Stat. 5)

Vietnam War: 1964-1973

Joint Resolution to promote the maintenance of international peace and security in southeast Asia (Gulf of Tonkin Resolution) (Joint Resolution of Aug. 10, 1964, Pub. L. No. 88-408, 78 Stat. 384)
To Amend the Foreign Military Sales Act, and for other Purposes (Repeal of the Gulf of Tonkin Resolution), Pub. L. No. 91-672, § 12, 84 Stat. 2053, 2055 (1971)
Memorandum from Richard G. Kleindienst, Deputy Attorney Gen., for the Director, Bureau of the Budget, "Effect of a Repeal of the Tonkin Gulf Resolution" (Jan. 15, 1970)
Orlando v. Laird, 443 F.2d 1039 (2d Cir. 1971) (determining that the Gulf of Tonkin Resolution was sufficient to authorize or ratify military activity in Vietnam and declining to consider the constitutionality of military action in Vietnam on political question grounds)
Massachusetts v. Laird, 451 F.2d 26 (1st Cir. 1971) (concluding that military action in Vietnam was not unconstitutional, in light of Congress's "steady" support through appropriations and other actions, and thus finding it unnecessary to decide the "boundaries" of the political branches' war powers)
Amendments to the Military Selective Service Act of 1967, Pub. L. No. 92-129, § 401, 85 Stat. 348, 360-61 (1971) (Mansfield Amendment) (declaring it to be "the sense of Congress that the United States terminate at the earliest practicable date all military operations of the United States in Indochina," stating provisions for withdrawal, and urging the President immediately to initiate negotiations with the government of North Vietnam)
Armed Forces Appropriation Authorization of 1972, Pub. L. No. 92-156, § 601, 85 Stat. 423, 430 (1971) (Mansfield Amendment) (see above)
Mitchell v. Laird, 488 F.2d 611 (D.C. Cir. 1973) (dismissing challenge to the constitutionality of military action in Vietnam on political question grounds)
Making Continuing Appropriations for the Fiscal Year 1974, and for Other Purposes, Pub. L. No. 93-52, § 108, 87 Stat. 130, 134 (1973) (prohibiting funding "directly or indirectly combat activities by United States military forces in or over or from off the shores" of North or South Vietnam, Laos, or Cambodia, after August 15, 1973; ban subsequently extended by Pub. L. No. 93-124; similar prohibitions in Pub. L. Nos. 93-50 and 93-126)

Cambodia: 1970

Memorandum from William H. Rehnquist, Assistant Attorney Gen., U.S. Dep't of Justice, to Charles W. Colson, Special Counsel to the President, "Presidential Authority to Permit Incursion Into Communist Sanctuaries in the Cambodia-Vietnam Border Area" (May 14, 1970)
Memorandum from William H. Rehnquist, Assistant Attorney Gen., U.S. Dep't of Justice, to Charles W. Colson, Special Counsel to the President, "The President and the War Power: South Vietnam and the Cambodian Sanctuaries" (May 22, 1970)
Special Foreign Assistance Act of 1971, Pub. L. No. 91-652, § 7, 84 Stat. 1942, 1943 (1971) (Cooper-Church Amendment) (prohibiting the use of authorized or appropriated funds to finance military intervention in Cambodia and stating that military and economic assistance "shall not be construed as a commitment by the United States to Cambodia for its defense")

The S.S. Mayaguez Rescue: 1975

Letter from Gerald Ford, President of the United States, to the Speaker of the House of Representatives and the President Pro Tempore of the Senate Reporting on United States Actions in the Recovery of the S.S. Mayaguez (May 15, 1975)

Iran: 1980

Letter from James Carter, Jr., President of the United States, to the Speaker of the House of Representatives and the President Pro Tempore of the Senate Reporting on the Operation (Apr. 26, 1980)
Dames & Moore v. Regan, 453 U.S. 654 (1981) (concluding that the President had authority to compel U.S. nationals to resolve claims against Iran through binding arbitration before a claims tribunal, because Congress was aware of and had acquiesced to the long-standing executive practice of settling claims by executive agreement and settlement was necessary to resolve a foreign policy dispute)

El Salvador: 1981

Crockett v. Reagan, 558 F. Supp. 893 (D.D.C. 1982) (dismissing challenge to military aid to El Salvador on political question grounds)

Lebanon: 1982-1983

Letter from Ronald Reagan, President of the United States, to the Speaker of the House of Representatives and the President Pro Tempore of the Senate on the Deployment of United States Forces in Beirut, Lebanon (Aug. 24, 1982)
Multinational Force in Lebanon Resolution (Joint Resolution of Oct. 12, 1983, Pub. L. No. 98-119, 97 Stat. 805)

Grenada: 1983

Letter from Ronald Reagan, President of the United States, to the Speaker of the House of Representatives and the President Pro Tempore of the Senate on the Deployment of United States Forces in Grenada (Oct. 25, 1983)
Conyers v. Reagan, 765 F.2d 1124 (D.C. Cir. 1985) (dismissing challenge to military action in Grenada on mootness grounds)

Libya: 1986

Letter from Ronald Reagan, President of the United States, to the Speaker of the House of Representatives and the President Pro Tempore of the Senate on the Gulf of Sidra Incident (Mar. 26, 1986)
Letter from Ronald Reagan, President of the United States, to the Speaker of the House of Representatives and the President Pro Tempore of the Senate on the United States Air Strike Against Libya (Apr. 16, 1986)

Persian Gulf: 1987-1988

Letter from Ronald Reagan, President of the United States, to the Speaker of the House of Representatives and the President Pro Tempore of the Senate on the United States Air Strike in the Persian Gulf (Sept. 24, 1987)
Ronald Reagan, President of the United States, Statement on United States Policy in the Persian Gulf (Sept. 24, 1987)
Lowry v. Reagan, 676 F. Supp. 333 (D.D.C. 1987) (dismissing challenge to reflagging operation in the Persian Gulf on equitable discretion and political question grounds)

Philippines: 1989

Letter from George H.W. Bush, President of the United States, to the Speaker of the House of Representatives and the President Pro Tempore of the Senate on United States Military Assistance to the Philippines (Dec. 2, 1989)

Panama: 1989-1990

Letter from George H.W. Bush, President of the United States, to the Speaker of the House of Representatives and the President Pro Tempore of the Senate on United States Military Action in Panama (Dec. 21, 1989)

Iraq: 1991

Letter from George H.W. Bush, President of the United States, to Congressional Leaders on the Deployment of United States Armed Forces to Saudi Arabia and the Middle East (Aug. 9, 1990)
Ange v. Bush, 752 F. Supp. 509 (D.D.C. 1990) (dismissing challenge to Gulf War on political question, equitable discretion, and ripeness grounds)
Dellums v. Bush, 752 F. Supp. 1141 (D.D.C. 1990) (dismissing challenge to military action on ripeness grounds)
Authorization for Use of Military Force Against Iraq Resolution (Joint Resolution of Jan. 14, 1991, Pub. L. No. 102-1, 105 Stat. 3)
George H.W. Bush, President of the United States, Statement on Signing the Resolution Authorizing the Use of Military Force Against Iraq (Jan. 14, 1991)
Letter from George H.W. Bush, President of the United States, to Congressional Leaders Transmitting a Report Pursuant to the Resolution Authorizing the Use of Force Against Iraq (Jan. 16, 1991)

Somalia: 1992-1993

Memorandum from Timothy E. Flanigan, Assistant Attorney Gen., to the Attorney General, "Memorandum Opinion for the Attorney General" (Dec. 4, 1992) (regarding authority to use U.S. military forces in Somalia)
Letter from William P. Barr, Attorney Gen., to the President of the United States (Dec. 4, 1992)
Letter from George H.W. Bush, President of the United States, to Congressional Leaders on the Situation in Somalia (Dec. 10, 1992)
Letter from William J. Clinton, President of the United States, to Congressional Leaders on the Situation in Somalia (June 10, 1993)
Department of Defense Appropriations Act, Pub. L. No. 103-139, § 8151, 107 Stat. 1418, 1475-77 (1993) (Byrd Amendment) (approving military operations in Somalia for certain limited purposes)
National Defense Authorization Act, Pub. L. No. 103-160, § 1512, 107 Stat. 1547, 1840-41 (1993) (Gephardt Amendment) (stating congressional policy regarding U.S. intervention in Somalia, including that the President "should by November 15, 1993, seek and receive congressional authorization in order for the deployment of United States forces in Somalia to continue")

Iraq: 1993

Bosnia: 1994-2004

Memorandum from Walter Dellinger, Assistant Attorney Gen., U.S. Dep't of Justice, to the Counsel to the President, "Proposed Deployment of United States Armed Forces into Bosnia" (Nov. 30, 1995)

Haiti: 1994-1995

Letter from Walter Dellinger, Assistant Attorney Gen., U.S. Dep't of Justice, to Sen. Robert Dole et al., "Deployment of United States Armed Forces into Haiti" (Sept. 27, 1994)

Liberia: 1996

Afghanistan and Sudan: 1998

Letter from William J. Clinton, President of the United States, to Congressional Leaders Reporting on Military Action Against Terrorist Sites in Afghanistan and Sudan (Aug. 21, 1998)

Yugoslavia: 1999 -

Campbell v. Clinton, 203 F.3d 19 (D.C. Cir. 2000) (dismissing challenge to Kosovo bombing campaign on standing grounds)
Memorandum from Randolph D. Moss, Assistant Attorney Gen., to the Attorney General, "Authorization for Continuing Hostilities in Kosovo" (Dec. 19, 2000)

Other 20th Century Statutes and Legal Documents About Military Action

Maritime Relations

Act to increase the revenue, and for other purposes (Act of Sept. 8, 1916, ch. 463, § 806, 39 Stat. 756, 799-800) (authorizing the President, during a war in which the United States is not engaged, to detain the vessels of any belligerent country that discriminates against U.S. traffic, citizens, or businesses, or refuses equal treatment to U.S. ships or citizens, and to use any necessary military force to do so)

United Nations

United Nations Participation Act (1945) (22 U.S.C. §§ 287–287e)
Memorandum from Walter Dellinger, Assistant Attorney Gen., Office of Legal Counsel, to Alan J. Kreczko, Special Assistant to the President and Legal Advisor to the National Security Council, "Placing of United States Armed Forces Under United Nations Operational or Tactical Control" (May 8, 1996)

War Crimes

War Crimes Act of 1996 (18 U.S.C. § 2441)

War Powers

War Powers Resolution of 1973 (50 U.S.C. §§ 1541–48)
President Richard Nixon, Veto of the War Powers Resolution, Pub. Papers 893, 893 (Oct. 24, 1973)

21st Century

Afghanistan and al Qaeda: 2001 -

Authorization for Use of Military Force (Joint Resolution of Sept. 18, 2001, Pub. L. No. 107-40, 115 Stat. 224)
Memorandum from John C. Yoo, Deputy Assistant Attorney Gen., U.S. Dep't of Justice, to the Deputy Counsel to the President, "The President's Constitutional Authority to Conduct Military Operations Against Terrorists and Nations Supporting Them" (Sept. 25, 2001)

Iraq: 2003-2011

Authorization for Use of Military Force Against Iraq Resolution of 2002 (Joint Resolution of Oct. 16, 2002, Public Law 107-243, 116 Stat. 1498)
Memorandum from Jay S. Bybee, Assistant Attorney Gen., U.S. Dep't of Justice, to the Counsel to the President, "Authority of the President Under Domestic and International Law to Use Military Force Against Iraq" (Oct. 23, 2002)
Doe v. Bush, 323 F.3d 133 (1st Cir. 2003) (dismissing challenge to military action in Iraq on ripeness grounds)

Haiti: 2004

Memorandum from Jack L. Goldsmith III, Assistant Attorney Gen., U.S. Dep't of Justice, to the Counsel to the President, "Deployment of United States Armed Forces to Haiti" (Mar. 17, 2004)

Libya: 2011

Memorandum from Caroline D. Krass, Principal Deputy Assistant Attorney Gen., U.S. Dep't of Justice, to the Attorney General, "Authority to Use Military Force in Libya" (Apr. 1, 2011)
Testimony of Harold Hongju Koh, Legal Advisor, U.S. Dep't of State, Before the Senate Foreign Relations Committee (June 28, 2011)
Letter from Barack Obama, President of the United States, to the Speaker of the House on the War Powers Resolution (June 15, 2011)
Kucinich v. Obama, 821 F. Supp. 2d 110 (D.D.C. 2011) (dismissing challenge to intervention in Libya on standing grounds)
Whitney v. Obama, 845 F. Supp. 2d 136 (D.D.C. 2012) (dismissing challenge to intervention in Libya on mootness grounds)

Other Resources

The Federalist No. 24 (Alexander Hamilton) (Congress's war powers)
The Federalist No. 25 (Alexander Hamilton) (need for a standing army)
The Federalist No. 69 (Alexander Hamilton) (President’s authority as Commander in Chief)

References

David J. Barron & Martin S. Lederman, The Commander in Chief at the Lowest Ebb --- Framing the Problem, Doctrine, and Original Understanding, 121 Harv. L. Rev. 689 (2008)
David J. Barron & Martin S. Lederman, The Commander in Chief at the Lowest Ebb --- A Constitutional History, 121 Harv. L. Rev. 941 (2008)
Amy Belasco, et al., Cong. Research Serv., RL33803, Congressional Restrictions on U.S. Military Operations in Vietnam, Cambodia, Laos, Somalia, and Kosovo: Funding and Non-Funding Approaches (2007), available at http://www.fas.org/sgp/crs/natsec/RL33803.pdf
Curtis A. Bradley & Jack L. Goldsmith, Congressional Authorization and the War on Terrorism, 118 Harv. L. Rev. 2047 (2005), available at http://www.uio.no/studier/emner/jus/humanrights/HUMR5503/h09/undervisningsmateriale/bradley_goldsmith.pdf
Curtis A. Bradley & Jack L. Goldsmith, Foreign Relations Law (4th ed. 2011) (especially ch. 4)
Jennifer K. Elsea & Richard F. Grimmett, Cong. Research Serv., RL31133, Declarations of War and Authorizations for the Use of Military Force: Historical Background and Legal Implications (2011), available at http://www.fas.org/sgp/crs/natsec/RL31133.pdf. This report contains an extensive list of domestic laws, including temporary emergency authorities, that are triggered or altered by war or national emergency. See pages 24-75.
Richard F. Grimmett, Cong. Research Serv., RL33532, War Powers Resolution: Presidential Compliance (2012), available at http://www.fas.org/sgp/crs/natsec/RL33532.pdf
Barbara Salazar Torreon, Cong. Research Serv., R42738, Instances of Use of United States Armed Forces Abroad, 1798-2013 (2013), available at http://www.fas.org/sgp/crs/natsec/R42738.pdf