While it is generally accepted that the Constitution grants war powers to the federal government, and the courts have never seriously questioned this, the source and division of war powers has been much disputed. Reasons for judicial acceptance of federal war powers include: that the power to declare war carries with it the power to conduct war ( McCulloch v. Maryland ); that the power to wage war derives from a country's sovereignty and is not dependent on the enumerated powers of the Constitution ( United States v. Curtiss-Wright Export Corporations, 1936); and that the power to wage war comes from the expressed powers as well as the necessary and proper clause. With such acceptance of the federal government's central role in war (and foreign policy generally), the Supreme Court has been reluctant to place any limits on the powers Congress or the president devise to conduct it. The courts have declared some statutes created during wartime unconstitutional, but in nearly every case it has been done on grounds that the law abused a power other than war power, and the decision has been rendered only after combat has ceased.
It is perhaps surprising that Congress has declared war on only five occasions: the War of 1812; the Mexican War; the Spanish-American War, World War I, and World War II. When U.S. involvement in other international conflicts was challenged in the courts, the judiciary has ruled that declaration is not required. For example, in Bas v. Tingy (1800), the Supreme Court held that Congress need not declare full-scale war and could engage in a limited naval conflict with France. During the latter half of the twentieth century the United States engaged in numerous military conflicts without declaring war, the most controversial being the Vietnam War. Lower courts ruled that the absence of a formal declaration of war in Vietnam raised political questions not resolvable in the courts. The Supreme Court refused all appeals to review the lower court rulings, although not all its denials were unanimously agreed (for example, Mora v. McNamara, 1967).
The courts have also rebuffed state challenges to federal government war-related actions. In 1990 the Supreme Court upheld a law in which Congress eliminated the requirement that governors consent before their states' National Guard units are called up for deployment ( Perpich v. Department of Defense, 1990). Specifically, Minnesota objected to National Guard units being sent to Honduras for joint exercises with that country's military. The issue was between states' control over the National Guard under the Constitution's militia clauses and congressional authority to provide trained forces. The unanimous decision in Perpich further strengthened the power of the federal government in military affairs.
While there has been little disagreement on the federal government's authority to go to war, the appropriate roles of Congress and the president have sparked considerable debate. Article 2, Section 2 of the Constitution begins: "The President shall be Commander in Chief of the Army and Navy of the United States, and of the Militia of the several States, when called into the actual Service of the United States." This sentence has been the source of controversy between the three branches of government. Of particular concern are the circumstances under which the president can authorize the use of force abroad and how and whether Congress should be involved in making such decisions. The role of the judiciary in such matters seems crucial, but the courts have been unwilling participants in these debates.
While such abandonment of judicial review is questionable, there are a series of historical precedents to support the courts' approach. In 1795, Congress authorized the president to call out the militia of any state to quell resistance to the law. The Court sanctioned the president's discretion to determine when an emergency existed and subsequent calling of state militia. Several New England states challenged that law during the War of 1812, but the Supreme Court upheld the delegation of congressional authority as a limited power in Martin v. Mott (1827). In subsequent decades the Court and Congress regarded the president's war power as primarily military in nature. The Supreme Court has never opposed the president's authority as commander in chief to deploy forces abroad. However, during most of the nineteenth century Congress provided the initiative in foreign policy. When presidents in peacetime sought expansionist policies that threatened war, Congress stopped them.
Supreme Court decisions during the Civil War played a central role in shaping the courts' approach to war powers. Congress was in recess when hostilities broke out, so President Abraham Lincoln declared a blockade of Confederate ports, issued a proclamation increasing the size of the army and navy, ordered new naval ships, and requested funds from the Treasury to cover military expenditures. When Congress returned it adopted a resolution that approved the president's actions. However, owners of vessels seized during the blockade and sold as prizes brought suit, arguing that no war had been declared between the North and the South. The Supreme Court ruled in the Prize Cases (1863) that President Lincoln's actions in the early weeks of the war were constitutional, because the threat to the nation justified the broadest range of authority in the commander in chief.
Despite a narrow 5–4 ruling, the Prize Cases bolstered the powers of the presidency and shaped the tendency of the judiciary to abstain from rulings that would curb war powers. The Supreme Court's decisions, which interpreted broadly the powers of the president as commander in chief, marked the beginning of expansionary presidential actions during war. The national emergency of civil war required that the executive be able to exercise powers that might not be permitted during peacetime. Thus, Lincoln's decisions to declare the existence of a rebellion, call out state militia to suppress it, blockade southern ports, increase the size of the army and navy, and spend federal money on the war effort were not rebuked by the courts. Even the Emancipation Proclamation was issued under Lincoln's authority as commander in chief. Only Lincoln's suspension of habeas corpus in certain parts of the country earned a censure from the Supreme Court.
The world wars of the twentieth century provided opportunities for Presidents Woodrow Wilson and Franklin Roosevelt to push the constitutional envelope. As the United States entered World War I in 1917, President Wilson sought and obtained from Congress broad delegations of power to prepare for war and to mobilize the country. He used these powers to manage the country's economy, creating war management and production boards (coordinated by the Council of National Defense) to coordinate production and supply. His actions included taking over mines and factories, fixing prices, taking over the transportation and communications networks, and managing the production and distribution of food. Because the president had obtained prior congressional approval for these actions, there were no legal challenges to Wilson's authority during the war.
In a novel interpretation of the economic turmoil of the 1930s, President Roosevelt equated the challenge of the Great Depression to war. He sought wide executive-branch powers to address the economic crisis, but the Supreme Court was reluctant to sanction such authority during peacetime. However, once the United States entered World War II, Roosevelt was on more solid footing. Congress again delegated vast federal powers to the president to help win the war, and Roosevelt created many new administrative agencies to aid in the effort. There were very few objections on constitutional grounds, largely because the three branches assumed that the use of war powers by Lincoln and Wilson applied to the current conflict. The Supreme Court never upheld challenges to the authority of wartime agencies or to the authority of the 101 government corporations created by Roosevelt to engage in production, insurance, transportation, banking, housing, and other lines of business designed to aid the war effort. The Court also upheld the power of the president to apply sanctions to individuals, labor unions, and industries that refused to comply with wartime guidelines. Even the case of the removal and relocation of Japanese Americans was considered by the Supreme Court, which ruled that, because Congress had ratified Roosevelt's executive order as an emergency war measure, this joint action was permitted.
The assertion of broad emergency powers by Presidents Wilson and Roosevelt obfuscated the constitutional separation between Congress's authority to declare war and the president's power to wage it. As long as Congress delegated authority to the president and appropriated funds (through its "power of the purse") to support such powers, the judiciary would interpret this as congressional sanction of the president's decision. The courts would not challenge this "fusion" of the two branches' warmaking powers.
The onset of the Cold War did not result in a curb in executive war powers. In 1950, President Harry Truman decided to commit U.S. forces to help South Korea without a declaration of war from Congress. He based the authority for his actions on the United Nations Security Council vote to condemn North Korea's invasion and urge member countries to assist South Korea. However, the Supreme Court ruled that President Truman went too far when he ordered the secretary of commerce to seize and operate most of the country's steel mills to prevent a nationwide strike of steelworkers. The president justified his actions by arguing that the strike would interrupt military production and cripple the war effort in Korea and by claiming authority as commander in chief. In Youngstown Sheet and Tube Company v. Sawyer (1952), also known as the Steel Seizure Case, the Court agreed that the president had overstepped constitutional bounds, but it did not rule out the possibility that such seizures might be legal if done with the consent of Congress. Nonetheless, the Steel Seizure Case is significant as the strongest rebuke by the Court of unilateral presidential national security authority. The country was at war when Truman acted, and Congress had not expressly denied him the authority to act. It was extraordinary for the Court to find that the president lacked authority under those circumstances.
Thus, the Cold War environment did little to curb the gradual expansion of presidential authority during war. In 1955, Congress authorized President Dwight D. Eisenhower to use force if necessary to defend Taiwan if China attacked the island. In 1962, President John F. Kennedy obtained a joint congressional resolution authorizing him to use force if necessary to prevent the spread of communism in the Western Hemisphere. Two years later, Congress passed the Gulf of Tonkin Resolution, which empowered President Lyndon B. Johnson to take all necessary steps, including the use of armed force, to assist in the defense of members of the Southeast Asia Collective Defense Treaty. President Johnson relied on this resolution to wage the war in Vietnam instead of asking Congress to declare war on North Vietnam. Federal courts were asked repeatedly during the late 1960s and early 1970s to rule on the constitutionality of the war. The Supreme Court declined to hear such cases on the view that war was a political question. Although opponents of the war contended that U.S. involvement was unconstitutional because Congress had never declared war, the legislative body continued to appropriate funds for defense, thus implying support for Johnson's, and then Richard Nixon's, policies in Southeast Asia.