Who decides defense and foreign affairs

Authority over defense and foreign affairs in the United States is divided by the Constitution between Congress and the President, with states holding a small, specific role through the National Guard. Congress declares war, raises and funds the armed forces in appropriations that cannot run longer than two years for the Army, regulates foreign commerce, and, through the Senate, approves treaties by a two thirds vote; the President is commander in chief and conducts diplomacy. This page explains how those powers work in law and in practice, with statutes such as the War Powers Resolution, so a priority or opinion can be pointed at the body that actually decides.

In plain words

The Constitution splits war and peace between two branches on purpose.

Congress controls the money and has the power to declare war. The Senate must approve treaties. The President commands the military and talks to other countries.

In real life, Presidents have used force many times without a declaration of war. Congress passed a law in 1973 to require reports and time limits, but every President since has said parts of it are unconstitutional.

States have a small role. Governors normally command their National Guard, but the President can call the Guard into federal service in some situations.

Voters have no direct vote on war, treaties, or the defense budget. Their voice comes through who they elect and what they tell those people.

Defined terms

Declaration of war. A formal act of Congress under Article I, Section 8, stating that the United States is at war.

Authorization for use of military force (AUMF). A statute in which Congress authorizes military action without formally declaring war.

Commander in chief. The President’s constitutional role as head of the armed forces.

Treaty. An international agreement made by the President with the advice and consent of two thirds of the Senators present.

Appropriation. A law providing money from the Treasury for a specified purpose. No defense program can be funded without one.

National Defense Authorization Act (NDAA). The annual law that sets defense policy and authorizes funding levels; the money itself comes through appropriations.

War Powers Resolution. The 1973 law (P.L. 93-148) requiring presidential reports and setting time limits on uses of force not authorized by Congress.

Congress: war, armies, money, and commerce

Defense and foreign affairs powers granted to Congress appear in Article I, Section 8. Congress has the power “to declare war, grant letters of marque and reprisal, and make rules concerning captures on land and water”; to “raise and support armies,” with no appropriation for that use “for a longer term than two years”; to “provide and maintain a navy”; to “regulate commerce with foreign nations”; and to “provide for calling forth the militia to execute the laws of the union, suppress insurrections and repel invasions”.⁠¹

The money power is the one Congress uses most. Each year it considers an NDAA and a defense appropriations bill. For fiscal 2027, the Congressional Research Service reports that the House Armed Services Committee reported its NDAA (H.R. 8800) on June 15, 2026, the House passed an amended version on July 22, the Senate Armed Services Committee reported S. 4784 on June 15, and the House Appropriations Committee reported its defense bill (H.R. 9495) on June 26; neither the NDAA nor the appropriation had been enacted as of the report’s September 3, 2026 update.⁠²

Congress also reviews major arms sales. Under 22 U.S.C. 2776(b), a letter of offer for a covered sale generally cannot be issued until 30 calendar days after Congress receives the certification (15 days for NATO members, Japan, Australia, South Korea, Israel, and New Zealand), and Congress may block the sale by enacting a joint resolution “prohibiting the proposed sale.” The President can waive the waiting period by certifying an emergency.⁠³ Because a joint resolution can be vetoed, blocking a sale in practice requires a two thirds majority in both chambers to override.

The President: command and diplomacy

Defense and foreign affairs authority granted to the President in Article II, Section 2 makes the President “commander in chief of the Army and Navy of the United States,” and of state militias when called into federal service, and gives the power to make treaties with the advice and consent of the Senate, “provided two thirds of the Senators present concur”.⁠⁴ The President also appoints ambassadors (with Senate confirmation), receives foreign ambassadors, and directs the departments of State and Defense.

The War Powers Resolution in law and practice

Defense and foreign affairs disputes between the branches center on when the President may use force without congressional approval. The War Powers Resolution, enacted November 7, 1973, over President Nixon’s veto,⁠⁵ requires the President, absent a declaration of war, to report to Congress within 48 hours when forces are introduced into hostilities or into situations where hostilities are clearly imminent, among other circumstances.⁠⁶ Within 60 calendar days of a report that is submitted or required, the President must end the use of force unless Congress has declared war, enacted a specific authorization, or extended the period; the President may extend it by up to 30 days by certifying that unavoidable military necessity requires it for the safe withdrawal of forces.⁠⁷

In practice, the Congressional Research Service reports that Presidents submitted 168 reports under the Resolution from 1975 through March 2017, that every President since enactment has taken the position that the Resolution is an “unconstitutional infringement” on the commander in chief’s authority, and that a report citing the section that starts the 60-day clock has been submitted only once, for the 1975 Mayaguez incident, after the action had already ended.⁠⁵

Much modern military action has rested instead on statutory authorizations. The 2001 Authorization for Use of Military Force, enacted September 18, 2001, authorizes the President “to use all necessary and appropriate force against those nations, organizations, or persons” the President determines planned, authorized, committed, or aided the September 11 attacks, or harbored such organizations or persons.⁠⁸ Whether that authorization should be repealed, narrowed, or replaced is a recurring debate in Congress.

States, governors, and the National Guard

Defense and foreign affairs is almost wholly federal, but states hold one important role. National Guard units normally serve under their governors. Under 10 U.S.C. 12406, the President may call Guard members into federal service when the United States “is invaded or is in danger of invasion by a foreign nation,” when there is “a rebellion or danger of a rebellion against the authority of the Government of the United States,” or when the President “is unable with the regular forces to execute the laws of the United States”; such orders “shall be issued through the governors of the States”.⁠⁹ Separately, the Posse Comitatus Act, 18 U.S.C. 1385, makes it a crime to willfully use the Army, Navy, Marine Corps, Air Force, or Space Force to execute the laws “except in cases and under circumstances expressly authorized by the Constitution or Act of Congress”.⁠¹⁰ When and how these provisions apply domestically is a contested legal question that courts continue to address.

Cities and counties have no formal foreign policy power, though they are affected by base locations, defense contracts, and the service of their residents.

Alliances and international commitments

Defense and foreign affairs commitments made through treaties bind the United States internationally. NATO’s member governments reaffirmed in June 2025 their commitment to collective defense under Article 5 of the Washington Treaty and agreed to a target of 5 percent of GDP for defense and related spending by 2035.⁠¹¹ Such targets are political commitments by governments; in the United States, actual spending still depends on annual acts of Congress.

Comparative notes

Defense and foreign affairs powers are allocated differently in other democracies. Germany’s Basic Law, for example, vests command of the armed forces in the “Federal Minister of Defence” (Article 65a, official translation) and provides that upon the declaration of a state of defense, command passes to the Federal Chancellor (Article 115b).⁠¹² A cabinet minister, not the head of state, holds command in ordinary times. Switzerland, by contrast, lets voters force referendums on many federal laws by collecting 50,000 signatures within 100 days of publication,⁠¹³ which gives Swiss voters a direct route to challenge some defense-related legislation that American voters lack.

Evidence

Defense and foreign affairs authority on this page is described from the constitutional text, the U.S. Code via the Legal Information Institute, the 2001 AUMF as published by Congress, NATO’s official declaration, and Congressional Research Service reports. The evidence page covers spending, costs, and outcomes.

Competing interpretations

Defense and foreign affairs authority is among the most contested constitutional questions in American history.

• Presidential view. Modern threats require speed and secrecy; the commander in chief clause and the executive’s role in foreign relations support broad authority to use force short of full-scale war, as every President since 1973 has maintained.⁠⁵
• Congressional view. The Constitution gave the war power to Congress precisely to make war harder to start; long-running reliance on old authorizations and unilateral action erodes that design.
• Functional view. The question is not which branch is right in principle but whether the system produces accountable decisions. Some argue that appropriations, oversight hearings, and elections already give Congress and the public strong levers if they choose to use them.

Application to this framework

Defense and foreign affairs proposals in My Vote Forward must name the deciding body, as every proposal does. For this subject that is almost always Congress or the President. A priority on defense can be routed to members of Congress representing participants’ districts; an opinion on a specific arms sale or authorization would carry the relevant statute and its timeline. Because voters do not vote on these questions directly, the link between participation and decision runs through representation, and the framework’s job is to make that link visible, not to pretend it is shorter than it is.

Unresolved questions

• Should the War Powers Resolution be revised, and if so, what time limits and reporting rules would both branches accept?
• How should old authorizations for use of force be reviewed, and should authorizations expire automatically?
• How can citizens hold representatives accountable on defense questions that are decided by large, complex bills with hundreds of provisions?