The judiciary's traditional refusal to be drawn into foreign policy matters has its origins in the Constitution, which established responsibility for exercising foreign policy with the executive and the legislature. The president as commander in chief is responsible for conducting war, but Congress is empowered to declare war and raise and maintain military forces. The president may negotiate treaties, but the Senate must ratify them. Congress appropriates funds for the president to use for international diplomacy. While Article 3, Section 2 of the Constitution extends judicial power to cases related to treaties, ambassadors, and the admiralty, and to controversies to which the United States is a party, there is no explicit constitutional role or responsibility for the judiciary in foreign affairs.
The lack of an enumerated constitutional power for the judiciary has not kept foreign policy questions out of the courts. The case of Marbury v. Madison (1803) established the Supreme Court's power of judicial review. This power has come to mean that the Court can determine whether legislative and executive branch actions are permitted within the powers outlined for these branches in the Constitution. Although the case details of Marbury were clearly domestic in nature, judicial review is applicable to all policy areas, including foreign policy.
Despite this power, the Supreme Court has often refused to review cases related to foreign affairs on the grounds that they are "political questions," which are solvable only by the political branches of government, Congress and the president. The Court first adopted this stance in Foster & Elam v. Neilson (1829), which involved an international dispute over title to part of the Louisiana Territory. In those cases it has heard, the Court generally has upheld exercise of the power in question—a power usually delegated by Congress to the president during a foreign affairs crisis.
Judicial abstention in questions involving foreign affairs is controversial. On the one hand, the Constitution provides no expressed powers for the judiciary in foreign affairs. The general foreign affairs powers distributed to the legislative and executive branches are clearly enumerated, although the specifics are vague and contradictory. Given the emotional nature of war, the absence of tools for the judiciary to apply its own foreign policy preferences, and its reliance on the executive to carry out a decision, deference is the only responsible approach for the courts to take. On the other hand is the argument that deference on political questions is an abdication of the judiciary's constitutional responsibilities. Article 3, Section 2 seems to bestow responsibility on the judiciary to review all cases under the laws and treaties of the United States. There is no exclusion for foreign policy, and treaties certainly are elements of foreign affairs. There is little in the Constitution to suggest that the framers regarded foreign affairs as privileged and beyond the safeguards established by the separation of powers. Yet at various times the Court has ruled the following to be political questions: matters of sovereignty of either the United States or another country; boundaries and territorial authority; the determination of U.S. neutrality; the existence of peace and war; the length of a military occupation; the recognition of the independence or belligerency of a foreign state or government; the acknowledgment of diplomatic immunity; the status of aliens; and the validity or breach of a treaty. The doctrine of political questions, then, must be seen as a product of judicial self-restraint.
The other side of the self-restraint coin is a willingness to let stand legislation that increases the authority of the other two branches, especially the executive, to shape foreign affairs. The courts often have used the "necessary and proper" clause of the Constitution (Article 1, Section 8) to permit congressional actions. Sometimes known as the "elastic clause," the necessary and proper clause has been interpreted broadly by the courts, beginning with McCulloch v. Maryland (1819), to give considerable discretion to the ways that the federal government, and in particular Congress, utilizes its expressed powers. In Missouri v. Holland (1920), the Supreme Court ruled that the necessary and proper clause could justify the supremacy of international treaties. Upset that lower courts had ruled a congressional act to protect migratory birds from hunters unconstitutional as a violation of state sovereignty, the federal government negotiated a treaty with Canada to protect the birds. Following Senate ratification of the treaty, Congress passed another law prohibiting hunting of the birds, using compliance with the U.S.–Canada treaty as its justification. In affirming the constitutionality of the second law under the necessary and proper clause, the Court opened itself to the criticism that the excuse to implement legislation to comply with international treaties circumvented constitutional restrictions on federal government power, thereby expanding federal authority.
Judicial deference is controversial on other grounds. In Harisiades v. Shaughnessy (1952), the Supreme Court heard an appeal brought by an alien being deported because of his membership in the Communist Party earlier in his life. The opinion of the Court was that policy toward aliens is a component of foreign relations, and that such matters "are so exclusively entrusted to the political branches of government as to be largely immune from judicial inquiry or interference." The decision was contentious because it did not appear that the Court had considered how restraint in reviewing political questions related to national security and foreign policy conflicts with other constitutional values and civil liberties.
Another justification for deference is that courts are not equipped with the expertise to rule on complicated foreign policy issues or treaties based on international law. It may be more expedient for domestic judges to rely upon the views of the executive branch. However, even in foreign policy cases, attorneys provide the necessary information in their roles as advocates. While deference may be the norm in cases with a foreign policy dimension, the judiciary has weighed in with important opinions at critical times in the country's history. Many of these moments occurred while the country was at war.