While war can be viewed as a specific component of foreign relations, foreign relations in general suffer from the same constitutional ambiguities as war. In addition to the president's commander in chief powers, the Constitution grants the president the power to make treaties and to receive and appoint ambassadors. Together, these grants of power are the source of the president's authority to conduct foreign policy. The Constitution's framers did not want the president to be as powerful as European monarchs in international matters, so Congress was given a voice too. While the president is free to negotiate treaties, they must be ratified by two-thirds of the Senate. Congress's only other constitutional authorizations over foreign policy derive from the powers mentioned earlier: the power to declare war, raise a military, and appropriate funds.
The judiciary has provided little guidance in more clearly demarcating executive and legislative branch powers in foreign policy, often invoking the political question doctrine. The result is that Court rulings either supported the actions of the political branches or refused to judge them. Baker v. Carr (1962) is the principle case outlining the Supreme Court's position on political questions. Although Baker v. Carr concerned the malapportionment of election districts in Tennessee, the Court's comments on political questions apply to domestic and foreign policy issues. Writing for the majority, Justice William Brennan outlined the circumstances under which a case involved a political question and the obligation of federal courts to abstain from ruling. Among other instances, Justice Brennan opined that judicial abstention would be appropriate whenever a case raised foreign policy questions that "uniquely demand single-voiced statement of the Government's views." Despite this attempt at clarification, Baker v. Carr continued to confuse constitutional scholars and lower courts because the guidelines set forth by Justice Brennan did little to clarify the definition of political questions, the circumstances under which an issue is nonjusticiable, or the approach the courts should take when confronted by cases that appear political and nonjusticiable.
For several reasons, then—an explicit constitutional role for Congress confined to treaties, the exclusion of individual states from traditional foreign policy, and judicial deference to the political branches in such matters—the president and executive branch have been the principle beneficiaries of Court rulings in foreign policy matters. United States v. Curtiss-Wright Export Corporation (1936) was a landmark case that confirmed the president's lead role in foreign affairs. In this case, Congress approved a joint resolution authorizing President Roosevelt to embargo arms shipments to Paraguay and Bolivia, if doing so might contribute to ending the war. After Roosevelt declared an embargo in effect, Curtiss-Wright was subsequently convicted of selling weapons to Bolivia in violation of the embargo. The company challenged the constitutionality of the resolution, arguing that it was an improper delegation of congressional power to the president.
Given that the Court had already struck down major New Deal programs, there was some expectation that it would do the same with respect to arms embargoes. However, in his 7–1 majority opinion, Justice George Sutherland presented an original and controversial defense of presidential authority in foreign affairs. Sutherland argued that independence from Britain fused the thirteen original colonies into a sovereign nation. He also distinguished between internal (domestic policy) and external (foreign policy) powers of the federal government. Internal powers, he argued, lay with the individual states and are conferred upon the federal government by the Constitution. External powers, however, derive the sovereignty that all countries enjoy, and sovereignty was passed from Britain to the union of states upon independence. Since the powers of the United States to conduct its foreign relations do not derive from, nor are enumerated in, the Constitution, it is impossible to identify or infer them from constitutional language. As a result, the Court's view was that delegation of power to the president in foreign affairs was not to be judged by the same standards as delegation of power over domestic matters. Consequently, the "president alone has the power to speak as a representative of the nation."
Sutherland's opinion is open to criticism from several angles. If the federal government derives powers from sources other than the Constitution, neither the Constitution nor the courts provide guidance in the distribution of such powers between the branches. The implication that foreign affairs powers of the federal government are extra-constitutional goes beyond previous Court opinions that, less controversially, found foreign affairs powers to be vested in the federal government by the Constitution. Further, the notion that the federal government was to have major powers outside the Constitution is not insinuated in the document itself, the records of the Constitutional Convention, the Federalist Papers, or contemporary debates. Sutherland's opinion is grounded in sovereignty, but it is also possible to interpret the Declaration of Independence as creating thirteen sovereign states, and many did conduct their own foreign relations until the Articles of Confederation. Sutherland's reliance on political philosophy and international law, rather than constitutional interpretation, as a basis for foreign policy powers is also controversial. Finally, drawing a clear distinction between foreign and domestic policy is becoming increasingly difficult to do, and an approach that derives different sources of power for each is bound to generate legal challenges. Sutherland's position holds up best if one takes the view that the Constitution is a document whose principle objective is to distribute power between the states and federal government, and among the branches of the federal government. Despite the criticisms, Curtiss-Wright is a landmark case in the broadening of federal and, in particular, presidential authority in foreign affairs.
Presidents have found additional means to increase their foreign policy powers. One is to use executive agreements, since they do not require Senate ratification but have been held by the Court to have the same legal status as treaties ( United States v. Pink, 1942). Executive agreements are of two forms: those authorized by Congress and those made on presidential initiative. Authorized executive agreements have provided authority for presidents to negotiate the lowering of tariff barriers and trade agreements. The Lend-Lease Act (1941) granted President Roosevelt the power to enter into executive agreements that would provide war material to "any country deemed vital to the defense of the United States." Numerous executive agreements have been negotiated regarding the stationing of U.S. military forces in other countries. Executive agreements made on presidential initiative have often been obtained during international conflict, including the ending of the Spanish-American War and the deployment of troops during China's Boxer Rebellion. The Supreme Court, in United States v. Belmont (1937), upheld Roosevelt's use of an executive agreement to formalize his decision to recognize the Soviet Union, noting that it had the effect of a treaty and overruled conflicting state laws. Roosevelt used executive agreements extensively in the years leading up to World War II and to negotiate agreements at the Cairo, Tehran, and Yalta conferences. President Lyndon Johnson made many secret agreements with Asian countries during the 1960s, and President Jimmy Carter used executive agreements that constituted the financial arrangement necessary to free American hostages in Iran. In Dames & Moore v. Regan (1981), the Supreme Court ruled that Presidents Carter and Reagan had acted consistently with emergency powers granted by statute to use executive agreements to suspend the financial claims of Americans against Iran, in return for the safe release of the hostages seized during the 1979 Iranian revolution.
While the treaty approval process is described in the Constitution and has raised few problems, the relationship between treaties, domestic laws, and the Constitution is less clear. One area of confusion was whether treaties were superior to national legislation. In Foster & Elam v. Neilson (1829), Chief Justice John Marshall distinguished between a self-executing treaty and a non-self-executing treaty. The former requires no legislation to put it into effect, while the latter does not take effect until implemented through legislation approved by the Congress and president. The superiority of a treaty or statute is determined by whichever is most recent. However, in the case of a non-self-executing treaty, congressional acts take precedence (Head Money Cases, 1884). In Missouri v. Holland (1920), the Court's ruling illustrated how treaties could increase the power of the federal government visà-vis the states. The Court upheld the national law protecting migratory birds on the grounds that it was necessary to carry the provisions of this non-self-executing treaty into effect.
The Court has also considered the termination of treaties. It has held that termination requires an act of Congress. If international obligations are violated as a result of the termination, the matter will need to be renegotiated with the international parties. However, the Court has also ruled that treaties may be terminated by agreement between the contracting parties, by treaty provisions, by congressional repeal, by the president, and by the president and Senate acting jointly. When President Carter decided to officially recognize the government of the People's Republic of China, he unilaterally terminated a mutual defense treaty between the United States and Taiwan. The Supreme Court refused to hear a case brought by Senator Barry Goldwater and nineteen other senators ( Goldwater v. Carter, 1979) asking the Court to require the president to first obtain congressional authorization.
It is clear that, for two centuries, the courts have played an important role in resolving foreign policy disputes between the executive and legislative branches. But this is only one of the two principle divisions of power established by the Constitution. The other principle is dividing power between the states and federal government. Along this division, too, the courts have been required to resolve disputes over foreign policy powers.