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The President and the War Power: 

South Vietnam and the Cambodian Sanctuaries

Recognizing congressional sanction for the Vietnam conflict by the Gulf of Tonkin resolution, even 

though it was not in name or by its terms a formal declaration of war, the President’s determination 

to authorize incursion into the Cambodian border area by United States forces in order to destroy 

sanctuaries utilized by the enemy is the sort of tactical decision traditionally confided to the Commander in Chief in the conduct of armed conflict.

Only if the constitutional designation of the President as Commander in Chief conferred no substantive 

authority whatever could it be said that prior congressional authorization for such a tactical decision 

was required. Since even those authorities least inclined to a broad construction of the executive 

power concede that the Commander in Chief provision does confer substantive authority over the 

manner in which hostilities are conducted, the President’s decision to invade and destroy the border 

sanctuaries in Cambodia was authorized under even a narrow reading of his power as Commander in 

Chief.

May 22, 1970

MEMORANDUM OPINION FOR THE SPECIAL COUNSEL TO THE PRESIDENT*

The recent decision by President Nixon to use United States armed forces to 

attack sanctuaries employed by the North Vietnamese and the Viet Cong which 

were located across the Cambodian border from South Vietnam has raised the 

issue of the scope for the President’s power to conduct military operations such as 

those now underway in Southeast Asia. This memorandum addresses itself to that 

issue.

I. Division of the War Power by the Framers of the Constitution

The draftsmen of the Constitution clearly intended to divide the war power 

inhering in any sovereign nation between the President and Congress, and just as 

clearly did not intend to precisely delimit the boundary between the power of the 

Executive Branch and that of the Legislative Branch. They rejected the traditional 

power of kings to commit unwilling nations to war to further the king’s international political objectives. At the same time, they recognized the need for quick 

executive response to rapidly developing international situations.

The accommodation of these two interests took place in the session of the 

Constitutional Convention on Friday, August 17, 1787. The enumeration of the 

powers of Congress was in the process of being submitted to the delegates, and 

discussion occurred following the submission to vote of the draft language 

empowering Congress “to make war.”

 

* Editor’s Note: This memorandum was addressed to Charles W. Colson, Special Counsel to the 

President. The cover memorandum explained as follows: “Enclosed is an expanded version of the 

memorandum on Presidential power entitled The President and the War Power: South Vietnam and the 

Cambodian Sanctuaries. I am sending copies to Jack Stevenson and John Lehman.”
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The full text of the discussion, as reflected in Madison’s notes of the proceedings, is set forth as an appendix to this memorandum.* The upshot was that the 

authority conferred upon Congress was changed from the power “to make war” to 

the power “to declare war.” 3 The Papers of James Madison 1351–53 (Henry D. 

Gilpin ed., 1841) (“Madison Notes”). Charles Pinckney urged that the war-making 

power be confided to the Senate alone, id. at 1351, while Pierce Butler urged that 

the power be vested in the President, id. at 1352. James Madison and Elbridge 

Gerry then jointly moved to substitute the word “declare” for the word “make,” 

“leaving to the Executive the power to repel sudden attacks.” Id. John Sherman 

expressed a preference for “make” as opposed to “declare,” because the latter was 

too narrow a grant of power. However, he expressed the view that the grant of 

power to Congress to “make” war would nonetheless permit the Executive to repel 

attack, although not to commence war. Id. Gerry and George Mason opposed the 

giving of the power to declare war to the Executive. Id. Rufus King supported the 

substitution of the word “declare,” urging that the word “make” might be understood to mean “conduct” war, which latter was an executive function. Id. at 1353 

n.*.

With only New Hampshire dissenting, it was agreed that the grant to Congress 

should be of the power to declare war. Pinckney’s motion to strike out the whole 

clause, and thereby presumably to leave the way open to vest the entire warmaking power in the Executive, was then defeated by a voice vote. Id. at 1353.

The framers of the Constitution, in making this division of authority between 

the Executive and the Legislative Branches, were painting with a broad brush on a 

constitutional fabric, and not endeavoring to accomplish a detailed allocation of 

authority between the two branches. Nearly 200 years of practice under the 

constitutional system has given rise to a number of precedents and usages, 

although it cannot be confidently said that any sharp line of demarcation exists as 

a result of this history.

II. Recognition of Armed Conflict Short of “War”

Before turning to historical practice for the light which it throws upon the 

proper interpretation of the President’s power, it is well to first dispel any notion 

that the United States may lawfully engage in armed hostilities with a foreign 

power only if Congress has declared war. From the earliest days of the republic, 

all three branches of the federal government have recognized that this is not so, 

and that not every armed conflict between forces of two sovereigns is “war.” This 

fact affords no final answer to the constitutional question of the division of 

authority between the President and Congress in exercising the war power, but it 

 

* Editor’s Note: That appendix was not preserved in the OLC daybooks and so it is not included 

here. Instead we have inserted citations to the appropriate parts of Madison’s notes on the Constitutional Convention.
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323

does suggest that the effort to find an answer is not advanced by a mechanical 

application of labels to various fact situations.

Congress, during the so-called “undeclared war” with France which lasted from 

1798 to 1800, authorized limited use of this nation’s armed forces against those of 

France. The Fifth Congress authorized President Adams to take the following 

measures:

That the President of the United States shall be, and is hereby authorized to instruct the commanders of the public armed vessels which 

are, or which shall be employed in the service of the United States, 

to subdue, seize and take any armed French vessel, which shall be 

found within the jurisdictional limits of the United States, or elsewhere, on the high seas, and such captured vessel, with her apparel, 

guns and appurtenances, and the goods or effects which shall be 

found on board the same, being French property shall be brought 

within some port of the United States, and shall be duly proceeded 

against and condemned as forfeited . . . .

Act of July 9, 1798, ch. 68, § 1, 1 Stat. 578, 578.

The Supreme Court in a case arising out of this “undeclared war” described 

these differences between war and other armed conflicts as being differences 

between “solemn war” and “imperfect war”:

If it be declared in form, it is called solemn, and is of the perfect 

kind; because one whole nation is at war with another whole nation; 

and all the members of the nation declaring war, are authorized to 

commit hostilities against all the members of the other, in every 

place, and under every circumstance. In such a war all the members 

act under a general authority, and all the rights and consequences of 

war attach to their condition.

But hostilities may subsist between two nations more confined in 

its nature and extent; being limited as to places, persons, and things; 

and this is more properly termed imperfect war; because not solemn, 

and because those who are authorized to commit hostilities, act under special authority, and can go no farther than to the extent of their 

commission.

Bas v. Tingy (The Eliza), 4 U.S. (4 Dall.) 37, 40 (1800) (opinion of Washington, 

J.).

While the Court termed both forms of military action “war,” the distinction 

which it drew likewise separates the declared wars of the Twentieth Century, such 

as the two World Wars, and the undeclared armed conflicts such as have more 

recently occurred in Korea and in Southeast Asia. In both of the two World Wars,

the declarations of war were viewed by the Executive Branch to authorize 
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complete subjugation of the enemy, and some form of “unconditional surrender” 

on the part of the enemy was the announced goal of the allied nations. In Korea 

and Vietnam, on the other hand, the goals have been the far more limited ones of 

the maintenance of territorial integrity and of the right of self-determination.

As has been chronicled many times, the United States throughout its history has 

been involved in armed conflicts short of declared war, from the undeclared war 

with France in 1798–1800 to Vietnam. See, e.g., H.R. Rep. No. 82-127 (1951); 

H.R. Doc. No. 84-443 (1956); James Grafton Rogers, World Policing and the 

Constitution 92–123 (1945). The more significant of these involvements are 

separately discussed in a following section of this memorandum.

III. Designation of the President as Commander in Chief Is a 

Grant of Substantive Power

Because of the nature of the President’s power as Commander in Chief and 

because of the fact that it is frequently exercised in external affairs, there are few 

judicial precedents dealing with the subject. Such judicial learning as there is on 

the subject, however, makes it reasonably clear that the designation of the 

President as Commander in Chief of the Armed Forces is a substantive grant of 

power, and not merely a commission which entitles him to precedence in a 

reviewing stand.1

Chief Justice Marshall, writing for the Supreme Court in Little v. Barreme, 

concluded that the seizure of a ship on the high seas had not been authorized by an 

act of Congress. In the course of the opinion, he stated:

It is by no means clear that the President of the United States

whose high duty it is to “take care that the laws be faithfully executed,” and who is Commander in Chief of the armies and navies of the 

United States, might not, without any special authority for that purpose, in the then existing state of things, have empowered the officers commanding the armed vessels of the United States, to seize and 

 

1 A statement of Alexander Hamilton in The Federalist 69 has been quoted in support of the notion 

that the designation of the President as Commander in Chief does nothing more than place him at the 

head of the military establishment. The full text of Hamilton’s comment does not support such a 

narrow construction:

The President is to be Commander-in-Chief of the army and navy of the United States. 

In this respect his authority would be nominally the same as that of the King of Great 

Britain, but in substance much inferior to it. It would amount to nothing more than the 

supreme command and direction of the military and naval forces, as first general and 

admiral of the Confederacy; while that of the British king extends to the declaring of 

war and to the raising and regulating of fleets and armies—all which, by the Constitution under consideration, would appertain to the Legislature.

The Federalist No. 69, at 417–18 (Clinton Rossiter ed., 1961).
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send into port for adjudication, American vessels which were forfeited by being engaged in this illicit commerce.

6 U.S. (2 Cranch) 170, 177 (1804).

Justice Grier, speaking for the Supreme Court in its famous decision in the 

Prize Cases, likewise viewed the President’s designation as Commander in Chief 

as being a substantive source of authority on which he might rely in putting down 

rebellion:

Whether the President in fulfilling his duties, as Commander in 

Chief, in suppressing an insurrection, has met with such armed hostile resistance, and a civil war of such alarming proportions as will 

compel him to accord to them the character of belligerents, is a question to be decided by him, and this Court must be governed by the 

decisions and acts of the political department of the Government to 

which this power was entrusted. “He must determine what degree of 

force the crisis demands.” The proclamation of blockade is itself official and conclusive evidence to the Court that a state of war existed 

which demanded and authorized a recourse to such a measure, under 

the circumstances peculiar to the case.

67 U.S. (2 Black) 635, 670 (1862).

More recently, Justice Jackson, concurring in Youngstown Sheet & Tube Co. v. 

Sawyer, said:

We should not use this occasion to circumscribe, much less to 

contract, the lawful role of the President as Commander in Chief. 

I should indulge the widest latitude of interpretation to sustain his 

exclusive function to command the instruments of national force, at 

least when turned against the outside world for the security of our 

society.

343 U.S. 579, 646 (1952).

The limits of the President’s power as Commander in Chief are nowhere defined in the Constitution, except by way of negative implication from the fact that 

the power to declare war is committed to Congress. However, as a result of 

numerous occurrences in the history of the Republic, more light has been thrown 

on the scope of this power.

IV. Scope of President’s Power as Commander in Chief

The questions of how far the Chief Executive may go without congressional 

authorization in committing American military forces to armed conflict, or in 

deploying them outside of the United States and in conducting armed conflict 

already authorized by Congress, have arisen repeatedly throughout the Nation’s 
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history. The Executive has asserted and exercised at least three different varieties 

of authority under his power as Commander in Chief:

(a) Authority to commit military forces of the United States to armed 

conflict, at least in response to enemy attack or to protect the lives of 

American troops in the field;

(b) Authority of deploy United States troops throughout the world, 

both to fulfill United States treaty obligations and to protect American interests; and

(c) Authority to conduct or carry on armed conflict once it is instituted, by making and carrying out the necessary strategic and tactical 

decisions in connection with such conflict.

Congress has on some of these occasions acquiesced in the President’s action 

without formal ratification; on others it has ratified the President’s action; and on 

still others it has taken no action at all. On several of the occasions, individual 

members of Congress, and, at the close of the Mexican War, one house of 

Congress on a preliminary vote, have protested executive use of the armed forces. 

While a particular course of executive conduct to which there was no opportunity 

for the Legislative Branch to effectively object cannot establish a constitutional 

precedent in the same manner as it would be established by an authoritative 

judicial decision, a long continued practice on the part of the Executive, acquiesced in by the Congress, is itself some evidence of the existence of constitutional 

authority to support such a practice. United States v. Midwest Oil Co., 236 U.S. 

459 (1915). As stated by Justice Frankfurter in his concurring opinion in Youngstown Sheet & Tube:

The Constitution is a framework for government. Therefore the way 

the framework has consistently operated fairly establishes that it has 

operated according to its true nature. Deeply embedded traditional 

ways of conducting government cannot supplant the Constitution or 

legislation, but they give meaning to the words of a text or supply 

them.

343 U.S. at 610.

A. Commitment of Military Forces to Armed Conflict Without 

Congressional Authorization

President Jefferson, in 1801, sent a small squadron of American naval vessels 

into the Mediterranean to protect United States commerce against threatened 

attack by the Barbary pirates of Tripoli. In his message to Congress discussing his 
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action, Jefferson took the view that it would require congressional authorization 

for this squadron to assume an offensive, rather than a defensive, stance.

In May 1845, President Polk ordered military forces to the coasts of Mexico 

and to the western frontier of Texas (still at that time an independent republic) in 

order to prevent any interference by Mexico with the proposed annexation of 

Texas to the United States. Following annexation, Polk ordered General Zachary 

Taylor to march from the Nueces River, which Mexico claimed was the southern 

border of Texas, to the Rio Grande River, which Texas claimed was the southern 

boundary of Texas. While so engaged, Taylor’s forces encountered Mexican 

troops, and hostilities between the two nations commenced on April 25, 1846. 

While Polk two and a half weeks later requested a declaration of war from 

Congress, there had been no prior authorization for Taylor’s march south of the 

Nueces.

Justice Grier, in his opinion for the Supreme Court in the Prize Cases, commented on this fact, stating:

The battles of Palo Alto and Rasaca de la Palma had been fought 

before the passage of the act of Congress of May 13, 1846, which 

recognized “a state of war as existing by the act of the Republic of 

Mexico.”

67 U.S. at 668.

In 1854, President Pierce approved the action of a naval officer who bombarded Greytown, Nicaragua, in retaliation against a revolutionary government that refused to make reparations for damage and violence to United States citizens. This 

action was upheld by Samuel Nelson, then a judge of the Southern District of New 

York and later a Justice of the Supreme Court of the United States, in Durand v. 

Hollins, 8 F. Case. 111 (C.C.D.N.Y. 1860) (No. 4186). In his opinion in that case, 

Judge Nelson said:

As the executive head of the nation, the president is made the only legitimate organ of the general government, to open and carry on 

correspondence of negotiations with foreign nations, in matters concerning the interests of the country or of its citizens. It is to him, also, the citizens abroad must look for protection of person and of 

property, and for the faithful execution of the laws existing and 

intended for their protection. For this purpose, the whole executive 

power of the country is placed in his hands, under the constitution, 

and the laws passed in pursuance thereof. . . .

. . . Acts of lawless violence, or of threatened violence to the citizen or his property, cannot be anticipated and provided for; and for 

the protection, to be effectual or of any avail, may, not unfrequently, 

require the most prompt and decided action. . . .
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. . . The question whether it was the duty of the president to interpose for the protection of the citizens at Greytown against an irresponsible and marauding community that had established itself there, 

was a public political question, in which the government, as well as 

the citizens whose interests were involved, was concerned, and 

which belonged to the executive to determine; and his decision is final and conclusive, and justified the defendant in the execution of his 

orders given through the Secretary of the Navy.

Id. at 112.

In April 1861, President Lincoln called for 75,000 volunteers to suppress the 

rebellion by the southern states, and proclaimed a blockade of the Confederacy. 

The Supreme Court in the Prize Cases upheld the acts taken by President Lincoln 

prior to their later ratification by Congress in July 1861, saying:

If a war be made by invasion of a foreign nation, the President is 

not only authorized but bound to resist force by force. He does not 

initiate the war, but is bound to accept the challenge without waiting 

for any special legislative authority.

67 U.S. at 668.

In 1900 President McKinley sent an expedition of 5,000 United States troops as 

a component of an international force during the Boxer Rebellion of China. While 

Congress recognized the existence of the conflict by providing for combat pay, 

Act of Mar. 2, 1901, ch. 803, 31 Stat. 895, 903, it neither declared war nor 

formally ratified the President’s action. A federal court, however, reiterated the 

early recognition of limited or undeclared war:

In the present case, at no time was there any formal declaration of 

war by the political department of this government against either the 

government of China or the ‘Boxer’ element of that government. A 

formal declaration of war, however, is unnecessary to constitute a 

condition of war.

Hamilton v. McClaughry, 136 F. 445, 449 (C.C.D. Kan. 1905).

Presidents Theodore Roosevelt, Taft, and Wilson on more than one occasion 

committed American troops abroad to protect American interests. In November 

1903, President Roosevelt ordered the United States Navy to guard the Panama 

area and prevent Colombian troops from being landed in Panama in order to 

suppress the Panamanian insurrection against Colombia. In his annual report to 

Congress in 1912, President Taft reported the sending of some 2,000 Marines to 

Nicaragua (at the request of the President of Nicaragua) and the use of warships 

and troops in Cuba. H.R. Doc. No. 62-927, at 8–9, 21 (1912). He merely advised 

Congress of these actions without requesting any statutory authorization.
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President Wilson on two separate occasions committed American armed forces 

to hostile actions in Mexican territory. In April 1914, he directed a force of sailors 

and Marines to occupy the City of Vera Cruz, during the revolution in that 

country. The city was seized and occupied for seven months without congressional 

authorization. In 1916, Wilson ordered General Pershing and more than 10,000 

troops to pursue Pancho Villa, the Mexican outlaw, into Mexican territory 

following the latter’s raid on Columbus, New Mexico.

The most recent example of presidential combat use of American armed forces 

without congressional declaration of war, prior to the Vietnam conflict, was 

President Truman’s intervention in the Korean conflict. Following invasion of 

South Korea by North Koreans on June 25, 1950, and a request for aid by the 

United Nations (“UN”) Security Council (S.C. Res. 83, U.N. Doc. S/RES/83 (June 

27, 1950)), President Truman ordered the United States air and sea forces to give 

South Korean troops cover and support. He ordered the Seventh Fleet to guard 

Formosa. On June 30, the President announced that he had authorized the use of 

United States ground forces in the Korean War, following the collapse of the 

South Korean Army. Ultimately, the number of troops engaged in the Korean 

conflict reached 250,000, and the conflict lasted more than three years. President 

Truman’s action without congressional authorization precipitated the “Great 

Debate” in Congress which raged from January to April 1951.

While the President relied upon the UN Charter as a basis for his action, as well 

as his power as Commander in Chief, his action stands as a precedent for executive action in committing United States armed forces to extensive hostilities 

without any formal declaration of war by Congress.

The UN Charter as a result of its ratification by the Senate has the status of a 

treaty, but it does not by virtue of this fact override any constitutional provision. 

Though treaties made in pursuance of the Constitution under the Supremacy 

Clause may override a state statute, Missouri v. Holland, 252 U.S. 416 (1920), 

they may not override specific constitutional limitations, Geofroy v. Riggs, 133 

U.S. 258 (1890); Reid v. Covert, 354 U.S. 1 (1957). If a congressional declaration 

of war would be required in other circumstances to commit United States forces to 

hostilities of the extent and nature of those undertaken in Korea, the ratification of 

the UN Charter would not obviate a like requirement in the case of the Korean 

conflict. While the issue of presidential power which was the subject of the great 

debate in Congress was never authoritatively resolved, it is clear that Congress 

acquiesced in President Truman’s intervention in Korea. See David Rees, Korea: 

The Limited War (1964); Merlo J. Pusey, The Way We Go to War (1969).
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B. Deployment of United States Troops Throughout the World2

In February 1917, President Wilson requested from Congress authority to arm 

American merchant vessels. When that authority failed of passage in Congress as 

a result of a filibuster, Wilson proceeded to arm them without congressional 

authority, stating that he was relying on his authority as Commander in Chief.

Near the close of the First World War, President Wilson announced a decision 

to send American troops to Siberia. The troops so sent remained for over a year, 

with their withdrawal beginning in January, 1920. There was no congressional 

authorization for such disposition of troops, and the United States had not declared 

war on Russia.

In 1941, prior to Pearl Harbor, President Roosevelt utilized his power as Commander in Chief to undertake a series of actions short of war designed to aid the 

allied forces in the Second World War. On April 9, 1941, he made an agreement 

with the Danish Minister for the occupation of Greenland by American forces. In 

May 1941, Roosevelt issued a proclamation declaring an unlimited national 

emergency, and he ordered American naval craft to “sink on sight” foreign 

submarines found in the “defensive waters” of the United States. In July 1941, the 

President announced that United States forces would occupy Iceland in order to 

relieve British forces there, and that the Navy would perform convoy duty for 

supplies being sent to Great Britain under Lend-Lease. In September 1941, 

Roosevelt stated that he had given orders to the United States Army and Navy to 

strike first at any German or Italian vessels of war in American “defensive 

waters”; the following month, he decided to carry 20,000 British troops from 

Halifax to the Middle East in American transports.

President Truman’s decision in 1951 to send four United States divisions to 

Europe in discharge of the nation’s NATO commitment occasioned prolonged 

debate in Congress over his powers to take such action without congressional 

approval. Congress ultimately acquiesced in the President’s action without 

actually resolving the question, and all of President Truman’s successors have 

asserted and exercised similar authority.

C. Authority to Conduct or Carry on Armed Conflict Once It Has 

Been Lawfully Instituted

It has never been doubted that the President’s power as Commander in Chief 

authorizes him, and him alone, to conduct armed hostilities which have been 

lawfully instituted. Chief Justice Chase, concurring in Ex parte Milligan, said:

 

2 The line between “deploying” forces and “committing them to combat” may be razor thin. Had 

Zachary Taylor not encountered Mexican resistance below the Nueces, that example could be classified 

as a “deployment,” while if under the orders of President Franklin Roosevelt, discussed infra, American naval vessels had sunk on sight a German submarine in the mid-Atlantic, that example could be 

treated as a “commitment to armed conflict.”
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Congress has the power not only to raise and support and govern 

armies but to declare war. It has, therefore, the power to provide by 

law for carrying on war. This power necessarily extends to all legislation essential to the prosecution of war with vigor and success, except such as interferes with the command of the forces and conduct 

of campaigns. That power and duty belong to the President as commander-in-chief.

71 U.S. (4 Wall.) 2, 139 (1866) (emphasis supplied).

In the First World War, it was necessary to decide whether United States troops 

in France would fight as a separate command under General Pershing, or whether 

United States divisions should be incorporated in existing groups or armies 

commanded by French or British generals. President Wilson and his military 

advisers decided that United States forces would fight as a separate command.

In the Second World War, not only similar military decisions on a global scale 

were required, but also decisions that partook as much of political strategy as they 

did of military strategy: Should the United States concentrate its military and 

materiel resources on either the Atlantic or Pacific fronts to the exclusion of the 

other, or should it pursue the war on both fronts simultaneously? Where should the 

reconquest of allied territories in Europe and Africa which had been captured by 

the Axis powers begin? What should be the goal of the allied powers? Those who 

lived through the Second World War will recall without difficulty, and without the 

necessity of consulting works of history, that this sort of decision was reached by 

the allied commanders in chief, and chief executive officers of the allied nations, 

without (on the part of the United States) any formal congressional participation. 

The series of conferences attended by President Roosevelt around the world—at 

Quebec, Cairo, Casablanca, Teheran, Yalta, and by President Truman at Potsdam, 

ultimately established the allied goals in fighting the Second World War, including 

the demand for unconditional surrender on the part of the Axis nations.

Similar strategic and tactical decisions were involved in the undeclared Korean 

War under President Truman. Questions such as whether United States forces 

should not merely defend South Korean territory, but pursue North Korean forces 

by invading North Korea, and as to whether American Air Force planes should 

pursue North Korean and Chinese Communist planes north of the Yalu River, 

separating Red China from North Korea, were of course made by the President as 

Commander in Chief without any formal congressional participation.

V. Constitutional Practice Requires Executive to Obtain Sanction of 

Congress for Conduct of Major Hostilities

It is too plain from the foregoing discussion to admit of denial that the Executive, under his power as Commander in Chief, is authorized to commit American 

forces in such a way as to seriously risk hostilities, and also to actually commit 

them to such hostilities, without prior congressional approval. However, if the 
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contours of the divided war power contemplated by the framers of the Constitution 

are to remain, constitutional practice must include executive resort to Congress in 

order to obtain its sanction for the conduct of hostilities which reach a certain 

scale. Constitutional practice also indicates, however, that congressional sanction 

need not be in the form of a declaration of war.

In the case of the Mexican War which was brought about, if not initiated, by 

the Executive, the President requested and obtained a declaration of war. Congress, meeting in 1861 pursuant to the call of President Lincoln, ratified all of the 

actions he had taken on his own initiative, and apparently refrained from declaring 

war on the Confederate States only because it did not wish to recognize them as a 

sovereign nation.

However, as previously noted, the Fifth Congress authorized President Adams 

to take certain military action against France without going so far as to declare 

war. More recently, in connection with President Eisenhower’s landing of troops 

in Lebanon and with the Cuban missile crisis in 1962, Congress has given advance 

authorization for military action by the President without declaring war. Pub. L. 

No. 85-7, 71 Stat. 5 (1957); Pub. L. No. 87-733, 76 Stat. 697 (1962).

The notion that such advance authorization by Congress for military operations 

constitutes some sort of an invalid delegation of congressional war power simply 

will not stand analysis. A declaration of war by Congress is in effect a blank check 

to the Executive to conduct military operations to bring about subjugation of the 

nation against whom war has been declared. The idea that while Congress may do 

this, it may not delegate a lesser amount of authority to conduct military operations, as was done in the instances referred to above, is both utterly illogical and 

unsupported by precedent. While cases such as A.L.A. Schechter Poultry Corp. v. 

United States, 295 U.S. 495 (1935), hold that Congress in delegating powers to 

deal with domestic affairs must establish standards for administrative guidance, no 

such principle obtains in the field of external affairs. The Supreme Court in United 

States v. Curtiss-Wright Exp. Corp. made this distinction clear:

Whether, if the Joint Resolution had related solely to internal affairs it would be open to the challenge that it constituted an unlawful 

delegation of legislative power to the Executive, we find it unnecessary to determine. The whole aim of the resolution is to affect a situation entirely external to the United States, and falling within the 

category of foreign affairs. . . .

It will contribute to the elucidation of the question if we first consider the differences between the powers of the federal government 

in respect of foreign or external affairs and those in respect of domestic or internal affairs. That there are differences between them, 

and that these differences are fundamental, may not be doubted.

. . . .
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It results that the investment of the federal government with the 

powers of external sovereignty did not depend upon the affirmative 

grants of the Constitution. The powers to declare and wage war, to

conclude peace, to make treaties, to maintain diplomatic relations 

with other sovereignties, if they had never been mentioned in the 

Constitution, would have vested in the federal government as necessary concomitants of nationality. . . .

. . . .

In the light of the foregoing observations, it is evident that this 

court should not be in haste to apply a general rule which will have 

the effect of condemning legislation like that under review as constituting an unlawful delegation of legislative power. The principles 

which justify such legislation find overwhelming support in the unbroken legislative practice which has prevailed almost from the inception of the national government to the present day.

299 U.S. 304, 315, 318, 322 (1936).

What must be regarded as the high water mark of executive action without 

express congressional approval is, of course, the Korean War. Although Congress 

never expressly sanctioned the President’s action in committing United States 

forces in the hundreds of thousands to the Korean conflict, it repeatedly voted 

authorizations and appropriations to arm and equip the American troops. This is 

not to say that such appropriations are invariably the equivalent of express 

congressional approval; the decision as to whether limited hostilities, commenced 

by the Executive, should be sanctioned by Congress may be one quite different 

from the decision as to whether American troops already committed and engaged 

in such hostilities shall be equipped and supplied.

VI. Extent to Which Congress May Restrict by Legislation the 

Substantive Power Granted the President by Virtue of His Being 

Designated as Commander in Chief

While the President may commit armed forces of the United States to hostile

conflict without congressional authorization under his constitutional power as 

Commander in Chief, his authority exercised in conformity with congressional 

authority or ratification of his acts is obviously broader than if it stood alone. By 

the same token, Congress undoubtedly has the power in certain situations to 

restrict the President’s power as Commander in Chief to a narrower scope than it 

would have had in the absence of legislation. Chief Justice Marshall strongly 

intimates in his opinion in Little v. Barreme that the executive action directing the 

seizure of a ship on the high seas would have been valid had not Congress enacted 

legislation restricting the circumstances under which such a seizure was author-
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334

ized. Congress, exercising its constitutional authority to “make rules concerning 

captures on land and water,” may thus constrict the President’s power to direct the 

manner of proceeding with such captures.

Congress has similarly sought to restrain the authority of the President in the 

exercise of its power to “raise and support Armies.” U.S. Const. art. I, § 8, cl. 12. 

In the Selective Service and Training Act of 1940, it was provided that:

Persons inducted into the land forces of the United States under this 

Act shall not be employed beyond the limits of the Western Hemisphere except in the Territories and possessions of the United States, 

including the Philippine Islands.

Pub. L. No. 76-783, § 3(e), 54 Stat. 885, 886 (1940).

In the year following enactment of this law, President Roosevelt determined to 

send United States troops, including draftees, to Iceland in order to relieve British 

troops garrisoned there. He chose to strain geography, rather than the law, and 

obtained the opinion of what was apparently a minority-view geographer that 

Iceland was actually in the Western Hemisphere.

Very recently, Congress has enacted legislation providing that United States 

forces shall not be dispatched to Laos or Thailand in connection with the Vietnam 

conflict. This proviso was accepted by the Executive.

This is not to say, however, that every conceivable condition or restriction 

which Congress may by legislation seek to impose on the use of American 

military forces would be free of constitutional doubt. Even in the area of domestic 

affairs, where the relationship between Congress and the President is balanced 

differently than it is in the field of external affairs, virtually every President since 

Woodrow Wilson has had occasion to object to certain conditions in authorization 

legislation as being violative of the separation of powers between the Executive 

and the Legislative Branch.

3 The problem would be met in exacerbated form 

should Congress attempt by detailed instructions as to the use of American forces 

already in the field to supersede the President as Commander in Chief of the 

armed forces. Surely this is the thrust of Chief Justice Chase’s concurring opinion 

in Ex parte Milligan, quoted earlier in this text:

[Congressional] power necessarily extends to all legislation essential 

to the prosecution of war with vigor and success, except such as interferes with the command of the forces and conduct of campaigns. 

That power and duty belong to the President as commander-in-chief.

71 U.S. at 139.

 

3 All of those Presidents have stated in one way or another that just because Congress concededly 

may refrain from appropriating any money at all, it does not necessarily follow that it may attach 

whatever condition it desires to an appropriation which it does make.
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335

Nor is the manner in which armed hostilities may be terminated altogether free 

from doubt. All declared wars in our history have been customarily concluded by 

treaties negotiated by the President and ratified by the Senate. An effort in the 

Constitutional Convention to give Congress the power to declare “peace” as well 

as “war” was unanimously turned down at the session of August 17, 1787. 

3 Madison Notes at 1353.

VII. The Vietnam Conflict: Relation Between the Power of the 

President and the Power of Congress

The duration of the Vietnam conflict, and its requirements in terms of both men 

and materiel, have long since become sufficiently large so as to raise the most 

serious sort of constitutional question had there been no congressional sanction of 

that conflict. However, as is well known, the conflict in its present form began 

following an attack on U.S. naval forces in the Gulf of Tonkin in August 1964. At 

that time President Johnson took direct air action against the North Vietnamese, 

and he also requested Congress “to join in affirming the national determination 

that all such attacks will be met” and asked for “a resolution expressing the 

support of the Congress for all necessary action to protect our Armed Forces and 

to assist nations covered by the SEATO [Southeast Asia Treaty Organization]

Treaty.” H.R. Doc. No. 88-333, at 2 (1964).

On August 10, 1964, Congress passed the following resolution:

Resolved by the Senate and House of Representatives of the United States of America in Congress assembled, That the Congress approves and supports the determination of the President, as Commander in Chief, to take all necessary measures to repel any armed 

attack against the forces of the United States and to prevent further 

aggression.

Sec. 2. The United States regards as vital to its national interest 

and to world peace the maintenance of international peace and security in southeast Asia. Consonant with the Constitution of the United 

States and the Charter of the United Nations and in accordance with 

its obligations under the Southeast Asia Collective Defense Treaty, 

the United States is, therefore, prepared, as the President determines, 

to take all necessary steps, including the use of armed force, to assist 

any member or protocol state of the Southeast Asia Collective Defense Treaty requesting assistance in defense of its freedom.

Sec. 3. The resolution shall expire when the President shall determine that the peace and security of the area is reasonably assured 

by international conditions created by action of the United Nations 
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336

or otherwise, except that it may be terminated earlier by concurrent 

resolution of the Congress.

Pub. L. No. 88-408, 78 Stat. 384, 384 (1964).

In connection with this resolution, Congress noted that whatever the limits of 

the President’s authority acting alone might be, whenever Congress and the 

President act together “‘there can be no doubt’” of the constitutional authority. 

H.R. Rep. 88-1708, at 4 (1964) (committee report on Gulf of Tonkin resolution, 

quoting committee report on Formosa resolution).

Since that time, Congress has repeatedly adopted legislation recognizing the 

situation in Southeast Asia, providing the funds to carry out United States 

commitments there, and providing special benefits for troops stationed there. By 

virtue of these acts, and by virtue of the provision in the Gulf of Tonkin resolution 

as to the manner in which it may be terminated, there is long-standing congressional recognition of a continuing United States commitment in Southeast Asia.

4

President Nixon has continued to maintain United States troops in the field in 

South Vietnam, in pursuance of his policy to seek a negotiated peace which will 

protect the right of the South Vietnamese people to self-determination. The 

legality of the maintenance of these troops in South Vietnam, and their use to 

render assistance to the South Vietnamese troops in repelling aggression from the 

Viet Cong and the North Vietnamese, would admit of reasonable doubt only if 

congressional sanction of hostilities commenced on the initiative of the Executive 

could be manifested solely by a formal declaration of war. But the numerous 

historical precedents previously cited militate against such a formal type of 

reasoning.

A requirement that congressional approval of executive action in this field can 

come only through a declaration of war is not only contrary to historic constitutional usage, but as a practical matter could not help but curtail effective congressional participation in the exercise of the shared war power. If Congress may 

sanction armed engagement of United States forces only by declaring war, the 

possibility of its retaining a larger degree of control through a more limited 

approval is foreclosed. While in terms of men and materiel the Vietnam conflict is 

one of large scale, the objectives for which the conflict may be carried on, as set 

forth in the Gulf of Tonkin resolution, are by no means as extensive or allinclusive as would have resulted from a declaration of war by Congress. Con-

 

4

“Legislative history” surrounding the Gulf of Tonkin resolution may be cited for a number of 

varying interpretations of exactly what Congress was authorizing. In view of the very plain text of the 

resolution, which authorizes the use of military force “as the President determines” to assist Southeast 

Asian countries, including South Vietnam, in defense of their freedom, Pub. L. No. 88-408, § 2, 78 

Stat. at 384, it is all but impossible to argue that substantial military operations in support of the South 

Vietnamese against North Vietnam and the Viet Cong were not thereby authorized. The fact that 

Congress did not by adopting this resolution intend to declare war does not detract from this 

conclusion; the authority conferred by the resolution is a good deal short of that which would be 

conferred by a declaration of war.
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337

versely, however, there cannot be the slightest doubt from an examination of the 

language of the Gulf of Tonkin resolution that Congress expressly authorized 

extensive military involvement by the United States, on no less a scale than that 

now existing, by virtue of its adoption of this resolution. To reason that if the 

caption “Declaration of War” had appeared at the top of the resolution, this 

involvement would be permissible, but that the identical language without such a 

caption does not give effective congressional sanction to it at all, would be to treat 

this most nebulous and ill defined of all areas of the law as if it were a problem in 

common law pleading. Justice Grier, more than a century ago, in the Prize Cases

said:

This greatest of civil wars was not gradually developed by popular commotion, tumultuous assemblies, or local unorganized insurrections. However long may have been its previous conception, it 

nevertheless sprung forth suddenly from the parent brain, a Minerva 

in the full panoply of war. The President was bound to meet it in the 

shape it presented itself, without waiting for Congress to baptize it 

with a name; and no name given to it by him or them could change 

the fact.

67 U.S. at 668–69. If substance prevailed over form in establishing the right of the 

federal government to fight the Civil War in 1861, substance should equally 

prevail over form in recognizing congressional sanction for the Vietnam conflict 

by the Gulf of Tonkin resolution, even though it was not in name or by its terms a 

formal declaration of war.

Viewed in this context, the President’s determination to authorize incursion 

into the Cambodian border area by United States forces in order to destroy 

sanctuaries utilized by the enemy is the sort of tactical decision traditionally 

confided to the Commander in Chief in the conduct of armed conflict. From the 

time of the drafting of the Constitution it has been clear that the Commander in 

Chief has authority to take prompt action to protect American lives in situations 

involving hostilities. Faced with a substantial troop commitment to such hostilities 

made by the previous Chief Executive, and approved by successive Congresses, 

President Nixon has an obligation as Commander in Chief of the country’s armed 

forces to take what steps he deems necessary to assure their safety in the field. A 

decision to cross the Cambodian border, with at least the tacit consent of the 

Cambodian government, in order to destroy sanctuaries being utilized by North 

Vietnamese in violation of Cambodia’s neutrality, is wholly consistent with that 

obligation. It is a decision made during the course of an armed conflict as to how 

that conflict shall be conducted, rather than a determination that some new and 

previously unauthorized military venture shall be undertaken.

By crossing the Cambodian border to attack sanctuaries used by the enemy, the 

United States has in no sense gone to “war” with Cambodia. United States forces 

are fighting with or in support of Cambodian troops, and not against them. 
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338

Whatever protest may have been uttered by the Cambodian government was 

obviously the most perfunctory, formal sort of declaration. The Cambodian 

incursion has not resulted in a previously uncommitted nation joining the ranks of 

our enemies, but instead has enabled us to more effectively deter enemy aggression heretofore conducted from the Cambodian sanctuaries.

Only if the constitutional designation of the President as Commander in Chief 

conferred no substantive authority whatever could it be said that prior congressional authorization for such a tactical decision was required. Since even those 

authorities least inclined to a broad construction of the executive power concede 

that the Commander in Chief provision does confer substantive authority over the 

manner in which hostilities are conducted, the President’s decision to invade and 

destroy the border sanctuaries in Cambodia was authorized under even a narrow 

reading of his power as Commander in Chief.

WILLIAM H. REHNQUIST

Assistant Attorney General

Office of Legal Counsel