Federal enclave

In United States law, a federal enclave is a parcel of federal property within a state that is under the "Special Maritime and Territorial Jurisdiction of the United States". While these enclaves, which are used for all the many Federal governmental purposes, such as post offices, arsenals, dams; road; etc., usually are owned by the Government, the United States in many cases has received similar jurisdictional authority over privately owned properties which it leases, or privately owned and occupied properties which are located within the exterior boundaries of a large area (such as the District of Columbia and various national parks) as to which a State has ceded jurisdiction to the United States.

In 1960, the year of the latest comprehensive inquiry, 7% of federal property had enclave status. Of the land with federal enclave status, 57% (4% of federal property, almost all in Alaska and Hawaii) was under "concurrent" state jurisdiction. The remaining 43% (3% of federal property), on which some state laws do not apply, was scattered almost at random throughout the United States. In 1960, there were about 5,000 enclaves, with about one million people living on them.^: 146 While a comprehensive inquiry has not been performed since 1960, these statistics are likely much lower today, since many federal enclaves were military bases that have been closed and transferred out of federal ownership.

Since late 1950s, it has been an official federal policy that the states should have full concurrent jurisdiction on all federal enclaves, an approach endorsed by some legal experts.