Fort Leavenworth R. Co. v. Lowe 114 U.S. 525 (1885) The Fort Leavenworth Military Reservation was built on land was originally purchased by the Federal government from France (in the Louisiana Purchase), and was constructed before Kansas became a State. When Kansas became a State, nothing was said about the Fort. Kansas, like all States, came into the Union on an 'equal footing', this meant that they received sovereignty over all the land, including the Fort. The Federal government could have, as a condition of Statehood, asked to retain dominion over the Fort, but did not do so. A few years later, this omission was rectified, and the Kansas Legislature passed a law that ceded jurisdiction of the Fort to the Federal government. However, the Kansas law said that the State retained the right to tax property on the Fort. The Fort Leavenworth Railroad Co. operated a railroad that was entirely located inside the Fort. Kansas ordered the railroad to pay property taxes. The railroad objected, claiming that the property inside the base was exempt from taxation. The railroad argued that the Enclave Clause (Art. 1 §8, cl. 17) says that the Federal government has exclusive authority over all places purchased by the consent of the Legislature of the State for the construction of forts and similar buildings. So basically, the railroad argued that the Enclave Clause meant that the Federal government has exclusive jurisdiction on the Fort, and were the only ones who could tax the railroad. The Trial Court found for Kansas. The railroad appealed. The Appellate Court affirmed. The railroad appealed. The US Supreme Court affirmed and found that Kansas could tax the railroad. The US Supreme Court found that the Fort was not originally purchased with the consent of Kansas (since it wasn't a State). In addition, Kansas never ceded the right to tax to the Federal government. Therefore, the Enclave Clause is not applicable. Basically, even though the Enclave Clause says that the Federal government can acquire exclusive jurisdiction over land with the consent of the State Legislature, they could also acquire land in different ways, and those acquisitions may not come with exclusive jurisdiction. The Enclave Clause isn't all or nothing. The States can cede some powers, and retain others. Btw, today, only about 6% of Federal land is an enclave. The Court noted that, as a condition of admission to the Union, the Federal government could have required Kansas to cede all sovereignty related to the Fort, but did not do so. Note that while this case held that States can retain some authority over Federal land, they cannot retain direct authority over Federal facilities. So for example, in this case Kansas could tax the privately-owned railroad, but they would not have been allowed to tax buildings and facilities directly owned by the Federal government. There aren't very many modern cases regarding the Enclave Clause. It is much more common for the Federal government invoke a combination of the Property Clause and the Supremacy Clause to keep the States from regulating Federal land. For example, see Kleppe v. New Mexico (426 U.S. 529 (1976)).