Major Anderson Invades South Carolina:
“The following excerpt is from an article by Prof. Robert L. Preston of Leesburg, Va., which appeared in the New York Times of May 9, [1926] on the “Title to Governor’s Island—Rights of the Federal Government and the State of New York as Set Forth in the Old Statutes,” is a most remarkable and interesting statement about the legal status of Fort Sumter in 1861: “South Carolina in 1805 (Statutes at Large, Volume V, p. 501) provided as follows in regard to the cessions in Charleston Harbor:
“That, if the United States shall not, within three years from the passing of this act, and notification thereof by the governor of this State to the Executive of the United States, repair the fortifications now existing thereon, or build such other forts or fortifications as may be deemed most expedient by the Executive of the United States on the same,  and keep a garrison or garrisons therein, in such case this grant or cession shall be void and of no effect.”
It may be on interest to state that Fort Sumter not only was not completed within the three-year limit stipulated in the contract, but was not completed in 1861 when Major Anderson transferred his garrison from Fort Moultrie. Moreover, it had never been garrisoned until he occupied it. So that, having neither been completed not garrisoned according to the contract, either within the three years specified time, or, for that matter, by 1861,  Major Anderson occupied a piece of property that the United States had not the vestige of a right to occupy, and which was under the ownership, jurisdiction, and sovereignty of the State of South Carolina exclusively.  In other words, he invaded the State of South Carolina with his troops—unwittingly, it is true, and on orders, but in fact, at any rate.  Adverse possession even could not lie here in behalf of the United States, since the United States had not garrisoned it.”
(Fort Sumter in 1861, Confederate Veteran, September, 1926, page 325)