What is the treaty power?

The treaty power is vested in the President, acting jointly with the Senate, by Article II, Section 2, Clause 2 of the Constitution: the President 'shall have Power, by and with the Advice and Consent of the Senate, to make Treaties, provided two thirds of the Senators present concur.' Three structural features define how the formal treaty process operates. First, the power is presidential in initiation: the President negotiates treaty terms through diplomatic agents, signs the treaty text, and chooses whether to submit it to the Senate -- submission is a presidential act, and the President may decline to submit a signed treaty or may withdraw a submitted treaty from Senate consideration before the Senate acts. Second, the Senate's role is advice and consent, not ratification: the Senate may consent unconditionally, consent with reservations or conditions (which may require renegotiation with the foreign government before the President ratifies), or refuse consent. The President then exercises the final act of ratification -- formally binding the United States under international law -- only after the Senate has given its advice and consent. Common usage calls this process Senate 'ratification,' but the constitutional text allocates the ratifying act to the President; the Senate's resolution of advice and consent is a constitutional precondition, not itself the ratifying act. Third, the two-thirds threshold is computed from Senators present and voting, not from all 100 Senators; with a quorum of 51 Senators present, 34 of those present may defeat a treaty. This supermajority requirement makes the formal treaty process significantly harder to complete than ordinary legislation and is the structural reason why the treaty process has increasingly been supplemented or replaced by executive agreements and congressional-executive agreements. Article VI, Clause 2 -- the Supremacy Clause -- provides that all treaties made, or which shall be made, under the Authority of the United States, shall be the supreme Law of the Land, and the Judges in every State shall be bound thereby, any Thing in the Constitution or Laws of any State to the Contrary notwithstanding. A validly ratified treaty therefore preempts inconsistent state statutes and state constitutional provisions by force of the Supremacy Clause, without any additional federal legislation required.

Missouri v. Holland, 252 U.S. 416 (1920), established the outer reach of the treaty power's relationship to Congress's domestic legislative authority. The United States and Great Britain had concluded a Migratory Bird Treaty in 1916 for the protection of birds migrating between Canada and the United States. Congress enacted the Migratory Bird Treaty Act of 1918 to implement the treaty, imposing closed seasons and other restrictions on hunting migratory birds. The State of Missouri sued Ray Holland, a federal game warden, arguing that the statute invaded powers reserved to the states under the Tenth Amendment -- Missouri contended that migratory birds within its borders were a matter of state authority, and two lower courts had previously struck down an earlier attempt to regulate migratory birds as beyond Congress's Commerce Clause power acting alone. Justice Holmes, writing for the Court in a 7-2 decision (Justices Van Devanter and Pitney dissenting), held that the Migratory Bird Treaty Act was a constitutionally valid exercise of the power to implement a valid treaty under the Necessary and Proper Clause. Holmes reasoned that the treaty power is an independent, enumerated constitutional power -- it is not derived from or limited to the subject-matter bounds of Congress's Article I legislative powers. An act of Congress implementing a valid treaty is necessary and proper to carry the treaty power into execution, and it does not matter that an identical statute enacted independently of a treaty would exceed Congress's Article I authority. Holmes wrote that matters of genuinely international concern -- like the protection of migratory birds that cannot be confined to any one state's jurisdiction and whose protection requires coordinated international action -- are the natural subjects of treaty commitments, and a rule of constitutional law that would deprive the federal government of the ability to fulfill such obligations would leave essential national interests unprotected. Missouri v. Holland has never been overruled and remains the foundational precedent for the proposition that the treaty power can authorize domestic federal legislation on subjects that would otherwise fall within the reserved powers of the states, provided the underlying treaty is a genuine exercise of the power to conduct international relations.

Dames & Moore v. Regan, 453 U.S. 654 (1981), addressed a fundamental structural question: may the President conclude binding international agreements without going through the Article II treaty process, and if so, under what constitutional authority? The case arose from the Iranian hostage crisis. After Iranian students seized the United States Embassy in Tehran in November 1979 and held American diplomats hostage, the Carter and Reagan administrations negotiated the Algiers Accords of January 1981 as the framework for the release of the hostages. The accords required the United States to suspend all claims by American nationals and companies against Iran then pending in American courts and to transfer those claims to an international arbitral tribunal -- the Iran-United States Claims Tribunal -- established to adjudicate them. Dames & Moore, an engineering company with a judgment against Iranian government entities, challenged the executive orders implementing the suspension and transfer of claims as beyond the President's constitutional authority. Justice Rehnquist, writing for the Court, applied the three-zone framework established by Justice Jackson's concurrence in Youngstown Sheet & Tube Co. v. Sawyer, 343 U.S. 579 (1952). Jackson's framework organized executive power by its relationship to congressional action: Zone I (express or implied congressional authorization -- presidential power at its maximum, with the combined force of the President's own constitutional powers and congressional delegation), Zone II (congressional silence -- the President acts on his own constitutional authority in a twilight zone where power is shared or congressional inaction may be permissive), and Zone III (express or implied congressional prohibition -- presidential power at its lowest ebb, sustainable only if Congress has exceeded its own constitutional authority). The Court held that the suspension of claims and their transfer to the international tribunal was constitutional: Congress had historically authorized and acquiesced in executive settlement of international claims through executive agreements, and specific statutes passed in connection with the hostage crisis implied authorization for the President's actions. Dames & Moore established the constitutional framework for all categories of executive agreements -- sole executive agreements resting on the President's Article II powers alone, congressional-executive agreements authorized by prior or subsequent legislation, and claims-settlement agreements resting on historical practice -- as alternatives to the formal Article II treaty process. Because executive agreements lack the Article II ratification predicate, they do not preempt state law by force of the Supremacy Clause as Article II treaties do, and they are revocable by subsequent Presidents, creating structural incentives to use the formal treaty process for commitments that the parties intend to be more durable.

The self-executing versus non-self-executing treaty distinction determines whether a ratified treaty provision is directly enforceable as domestic law in American courts without additional implementing legislation from Congress. Medellin v. Texas, 552 U.S. 491 (2008), is the Supreme Court's most important modern decision on the doctrine. Jose Ernesto Medellin, a Mexican national convicted of capital murder in Texas and sentenced to death, argued that the United States was bound by a judgment of the International Court of Justice (ICJ) in the Avena case, which ruled that the United States had violated its consular-notification obligations under the Vienna Convention on Consular Relations -- the right of detained foreign nationals to notify their consulate -- with respect to 51 Mexican nationals including Medellin. President George W. Bush issued a memorandum directing state courts to give effect to the Avena judgment. Texas courts declined. Chief Justice Roberts, writing for a 6-3 Court, held on two independent grounds that neither the treaty nor the presidential memorandum required Texas courts to reopen Medellin's conviction. First, the Vienna Convention and the Optional Protocol providing for ICJ jurisdiction were not self-executing: determining whether a treaty provision is directly enforceable as domestic law requires examining the treaty text, context, and ratification history to find a plain statement of intent for direct domestic effect without implementing legislation. The Court applied the principle traceable to Chief Justice Marshall's opinion in Foster v. Neilson, 27 U.S. (2 Pet.) 253 (1829) -- that a treaty provision that 'addresses itself to the political, not the judicial department' is not judicially enforceable without legislative implementation. No such intent appeared in the Vienna Convention or the ICJ Statute: those instruments obligated the United States as a matter of international law but required Congress to enact domestic implementing legislation before they could be enforced in American courts against the procedural rules of state criminal proceedings. Second, the President's memorandum directing state courts to comply with the Avena judgment was not a valid exercise of executive power. The President may implement non-self-executing treaties through executive action when Congress has authorized that action, but there was no statutory or constitutional authority for the President to independently direct state courts to reopen concluded criminal proceedings by overriding state procedural default rules. The President's foreign-affairs power does not extend to creating new, enforceable domestic obligations on state courts without congressional legislation.

For the 2028 election, the treaty power will shape the new administration's conduct of foreign affairs in four principal domains. First, the advice-and-consent threshold: the two-thirds Senate advice-and-consent requirement computed from Senators present means the incoming President's ability to ratify new international commitments through the formal Article II treaty process depends on the Senate composition determined by the 2028 elections, including 33 Class II seats. A party with a majority of fewer than 67 Senators cannot guarantee treaty ratification without opposition support; a coalition of 34 present Senators can defeat treaty ratification even if a numerical majority favors consent. This supermajority threshold is the structural reason why Presidents have increasingly relied on executive agreements and congressional-executive agreements requiring only simple majorities or previously enacted Trade Promotion Authority. Second, executive agreement durability: Dames & Moore confirms that executive agreements concluded with congressional acquiescence are valid exercises of presidential authority, but they are revocable by subsequent Presidents without Senate action, and their preemptive force over state law under the Supremacy Clause is more limited than that of Article II treaties. The choice between an Article II treaty and an executive agreement for any new international commitment -- on climate, arms control, trade, or security -- will affect how durable that commitment is under future administrations. Third, NATO and existing treaty obligations: the North Atlantic Treaty was ratified by the Senate in 1949; the existing Article 5 mutual-defense commitment is a valid Article II treaty and binds the United States without requiring new Senate action for its continued operation; any significant modification or formal withdrawal from the treaty would require examining whether Senate advice and consent is constitutionally required. Fourth, trade agreements and implementing legislation: most major trade agreements since the 1970s have been implemented through congressional-executive agreements authorized by Trade Promotion Authority (fast-track) statutes, with implementing legislation passed by simple majorities in both chambers; the Medellin doctrine confirms that non-self-executing trade-agreement provisions require implementing statutes to bind domestic courts -- the 2028 Senate composition determines whether implementing legislation for any new trade commitment can be enacted with a simple-majority vote rather than a two-thirds threshold.