Under Article I, Section 8, Congress has the power to declare war, raise and support Armies, provide and maintain a Navy, and organize, arm, discipline, and call forth a militia. This power gives Congress quite broad authority to undertake any measures that Congress considers necessary for providing for the national defense in both peacetime and wartime. This includes the military draft and selective service systems as well as wage, price, and rent control of the civilian economy during wartime. Under Korematsu v. United States, 323 U.S. 214 (1944), this power also includes such restrictions on civilians as exclusion from certain areas during wartime.
Congress may set up military courts and tribunals. These courts are not Article III courts, so the procedural requirements are under the Bill of Rights such as a right to a jury trial are not required. Instead, under Article I, Section 8, Clause 14, the Uniform Code of Military Justice applies.
See Congressional power.