The Non-Detention Act of 1971 was passed to repeal portions of McCarran Internal Security Act

McCarran Internal Security Act

The Internal Security Act of 1950, , also known as the Subversive Activities Control Act or the McCarran Act, after Senator Pat McCarran , is a United States federal law of the McCarthy era. It was passed over President Harry Truman's veto...

 of 1950, , specifically Title II, the "Emergency Detention Act". It had allowed for detention of suspected subversives without the normal Constitutional checks required for imprisonment. The Non-Detention Act requires specific Congressional authorization for such detention. Passed as Public Law 92-128, 85 Stat. 347 (1971), it was codified at 18 U.S.C. § 4001(a).

§ 4001. Limitation on detention

(a) No citizen shall be imprisoned or otherwise detained by the United States except pursuant to an Act of Congress.

In recent years, the statute has been used to challenge military detainment of U.S. citizens accused of terrorist activity. A Congressional Research Service report on the history of the Non-Detention Act concluded,

Legislative debate, committee reports, and the political context of 1971 indicate that when Congress enacted Section 4001(a) it intended the statutory language to restrict all detentions by the executive branch, not merely those by the Attorney General. Lawmakers, both supporters and opponents of Section 4001(a), recognized that it would
restrict the President and military authorities.

The Supreme Court of the United States

Supreme Court of the United States

The Supreme Court of the United States is the highest court in the United States. It has ultimate appellate jurisdiction over all state and federal courts, and original jurisdiction over a small range of cases...

 originally took the case of Rumsfeld v. Padilla

Rumsfeld v. Padilla

Rumsfeld v. Padilla, , was a United States Supreme Court case, in which José Padilla sought habeas corpus relief against Secretary of Defense Donald Rumsfeld, as a result of his detainment as an "unlawful combatant."...

to decide the question of whether Congress's Authorization for Use of Military Force

Authorization for Use of Military Force

Authorization for Use of Military Force may refer to:*Authorization for Use of Military Force Against Iraq Resolution of 1991 authorizing the Persian Gulf War, also known as Operation Desert Storm: H.R.J. Res...

authorized the President to detain a U.S. citizen, but did not give an answer, instead ruling that the case had been improperly filed.