Found in Title 50, Chapter 33 of the US Code.
Thanks to the Legal Information Institute at Cornell.
§ 1541. Purpose and policy
(a) Congressional declaration
It is the purpose of this chapter to fulfill the intent of the framers of the Constitution of the United States and insure that the collective judgment of both the Congress and the President will apply to the introduction of United States Armed Forces into hostilities, or into situations where imminent involvement in hostilities is clearly indicated by the circumstances, and to the continued use of such forces in hostilities or in such situations.
(b) Congressional legislative power under necessary and proper clause
Under article I, section 8, of the Constitution, it is specifically provided that the Congress shall have the power to make all laws necessary and proper for carrying into execution, not only its own powers but also all other powers vested by the Constitution in the Government of the United States, or in any department or officer hereof.
(c) Presidential executive power as Commander-in-Chief; limitation
The 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 statutory authorization, or
(3) a national emergency created by attack upon the United States, its territories or possessions, or its armed forces.
§ 1542. Consultation; initial and regular consultations
The President in every possible instance shall consult with Congress before introducing United States Armed Forces into hostilities or into situations where imminent involvement in hostilities is clearly indicated by the circumstances, and after every such introduction shall consult regularly with the Congress until United States Armed Forces are no longer engaged in hostilities or have been removed from such situations.
§ 1543. Reporting requirement
(a) Written report; time of submission; circumstances necessitating submission; information reported
In the absence of a declaration of war, in any case in which United States Armed Forces are introduced—
(1) into hostilities or into situations where imminent involvement in hostilities is clearly indicated by the circumstances;
(2) into the territory, airspace or waters of a foreign nation, while equipped for combat, except for deployments which relate solely to supply, replacement, repair, or training of such forces; or
(3) in numbers which substantially enlarge United States Armed Forces equipped for combat already located in a foreign nation;
the President shall submit within 48 hours to the Speaker of the House of Representatives and to the President pro tempore of the Senate a report, in writing, setting forth—
(A) the circumstances necessitating the introduction of United States Armed Forces;
(B) the constitutional and legislative authority under which such introduction took place; and
(C) the estimated scope and duration of the hostilities or involvement.
(b) Other information reported
The President shall provide such other information as the Congress may request in the fulfillment of its constitutional responsibilities with respect to committing the Nation to war and to the use of United States Armed Forces abroad.
(c) Periodic reports; semiannual requirement
Whenever United States Armed Forces are introduced into hostilities or into any situation described in subsection (a) of this section, the President shall, so long as such armed forces continue to be engaged in such hostilities or situation, report to the Congress periodically on the status of such hostilities or situation as well as on the scope and duration of such hostilities or situation, but in no event shall he report to the Congress less often than once every six months.
§ 1544. Congressional action
(a) Transmittal of report and referral to Congressional committees; joint request for convening Congress
Each report submitted pursuant to section 1543 (a)(1) of this title shall be transmitted to the Speaker of the House of Representatives and to the President pro tempore of the Senate on the same calendar day. Each report so transmitted shall be referred to the Committee on Foreign Affairs of the House of Representatives and to the Committee on Foreign Relations of the Senate for appropriate action. If, when the report is transmitted, the Congress has adjourned sine die or has adjourned for any period in excess of three calendar days, the Speaker of the House of Representatives and the President pro tempore of the Senate, if they deem it advisable (or if petitioned by at least 30 percent of the membership of their respective Houses) shall jointly request the President to convene Congress in order that it may consider the report and take appropriate action pursuant to this section.
(b) Termination of use of United States Armed Forces; exceptions; extension period
Within sixty calendar days after a report is submitted or is required to be submitted pursuant to section 1543 (a)(1) of this title, whichever is earlier, the President shall terminate any use of United States Armed Forces with respect to which such report was submitted (or required to be submitted), unless the Congress
(1) has declared war or has enacted a specific authorization for such use of United States Armed Forces,
(2) has extended by law such sixty-day period, or
(3) is physically unable to meet as a result of an armed attack upon the United States. Such sixty-day period shall be extended for not more than an additional thirty days if the President determines and certifies to the Congress in writing that unavoidable military necessity respecting the safety of United States Armed Forces requires the continued use of such armed forces in the course of bringing about a prompt removal of such forces.
(c) Concurrent resolution for removal by President of United States Armed Forces
Notwithstanding subsection (b) of this section, at any time that United States Armed Forces are engaged in hostilities outside the territory of the United States, its possessions and territories without a declaration of war or specific statutory authorization, such forces shall be removed by the President if the Congress so directs by concurrent resolution.
§ 1545, 1546, and 1546a consider the procedures by which legislation authorizing or halting military action shall be considered in the Congress.
§ 1547. Interpretation of joint resolution
(a) Inferences from any law or treaty
Authority to introduce United States Armed Forces into hostilities or into situations wherein involvement in hostilities is clearly indicated by the circumstances shall not be inferred—
(1) from any provision of law (whether or not in effect before November 7, 1973), including any provision contained in any appropriation Act, unless such provision specifically authorizes the introduction of United States Armed Forces into hostilities or into such situations and states that it is intended to constitute specific statutory authorization within the meaning of this chapter; or
(2) from any treaty heretofore or hereafter ratified unless such treaty is implemented by legislation specifically authorizing the introduction of United States Armed Forces into hostilities or into such situations and stating that it is intended to constitute specific statutory authorization within the meaning of this chapter.
(b) Joint headquarters operations of high-level military commands
Nothing in this chapter shall be construed to require any further specific statutory authorization to permit members of United States Armed Forces to participate jointly with members of the armed forces of one or more foreign countries in the headquarters operations of high-level military commands which were established prior to November 7, 1973, and pursuant to the United Nations Charter or any treaty ratified by the United States prior to such date.
(c) Introduction of United States Armed Forces
For purposes of this chapter, the term “introduction of United States Armed Forces” includes the assignment of members of such armed forces to command, coordinate, participate in the movement of, or accompany the regular or irregular military forces of any foreign country or government when such military forces are engaged, or there exists an imminent threat that such forces will become engaged, in hostilities.
(d) Constitutional authorities or existing treaties unaffected; construction against grant of Presidential authority respecting use of United States Armed Forces
Nothing in this chapter—
(1) is intended to alter the constitutional authority of the Congress or of the President, or the provisions of existing treaties; or
(2) shall be construed as granting any authority to the President with respect to the introduction of United States Armed Forces into hostilities or into situations wherein involvement in hostilities is clearly indicated by the circumstances which authority he would not have had in the absence of this chapter.