<P> One aspect of federal jurisdiction is the extent of legislative power . Under the Constitution, Congress has power to legislate only in the areas that are delegated to it . Under clause 17 Article I Section 8 of the Constitution however, Congress has power to "exercise exclusive Legislation in all cases whatsoever" over the federal district (Washington, D.C.) and other territory ceded to the federal government by the states, such as for military installations . </P> <P> Federal jurisdiction in this sense is important in criminal law because federal law does not supersede state criminal law . Congress has enacted the Assimilative Crimes Act (18 U.S.C. § 13), which provides that any act that would have been a crime under the laws of the state in which a federal enclave is situated is also a federal crime . Per the Article 1 of the United States Constitution "Enclave Clause" the State must cede jurisdiction to the federal gov 't to establish a federal enclave, all cessions are recorded in state and federal law . As most such enclaves are occupied by the military, except large land masses such as Rocky Mountain National Park, military law is especially concerned with these enclaves, especially the issue of establishing who has jurisdiction and what type of jurisdiction . In such areas, the federal government may have a proprietorial interest only (rights as landowner), concurrent jurisdiction (with federal and state law applicable), or exclusive jurisdiction over the land where an act was committed . Courts - martial involving military members subject to the Uniform Code of Military Justice apply regardless of location . Some started to replace the term "proprietorial interest only", with "proprietary jurisdiction". This incorrectly implies that the federal government has obtained some form of legislative jurisdiction from the state . The correct and original term is "Proprietorial Interest Only". </P> <P> Article Four of the United States Constitution also states that the Congress has the power to enact laws respecting the Territory or other Property belonging to the United States . Federal jurisdiction exists over any territory thus subject to laws enacted by the Congress . </P> <P> The American legal system includes both state courts and federal courts . State courts hear cases involving state law, and such federal laws as are not restricted to hearing in federal courts . Federal courts may only hear cases where federal jurisdiction can be established . Specifically, the court must have both subject - matter jurisdiction over the matter of the claim and personal jurisdiction over the parties . </P>

Where does the federal legislative branch get its power to create federal crimes