Règle correspondante
United States of America
Practice Relating to Rule 106. Conditions for Prisoner-of-War Status
Section B. Levée en masse
The US Air Force Pamphlet (1976) provides:
A levée en masse need not be organized, under command, or wear a distinctive sign. However, members must carry arms openly and comply with the law of armed conflict. To be a lawful levée en masse, it must be a spontaneous response by inhabitants of a territory not under occupation to an invading force. Spontaneity requires that there be no time to organize into regular armed forces. 
United States, Air Force Pamphlet 110-31, International Law – The Conduct of Armed Conflict and Air Operations, US Department of the Air Force, 1976, § 3-2(b)(5); see also Field Manual 27-10, The Law of Land Warfare, US Department of the Army, 18 July 1956, as modified by Change No. 1, 15 July 1976, § 65.
The US Naval Handbook (2007) states:
Lawful combatants … include civilians who take part in a levee en masse. A levee en masse is a spontaneous uprising by the citizens of a nonoccupied territory who take up arms to resist an invading force without having time to form themselves into regular armed units. Combatant immunity for a levee en masse ends once the invading forces have occupied the territory. 
United States, The Commander’s Handbook on the Law of Naval Operations, NWP 1-14M/MCWP 5-12.1/COMDTPUB P5800.7, issued by the Department of the Navy, Office of the Chief of Naval Operations and Headquarters, US Marine Corps, and Department of Homeland Security, US Coast Guard, July 2007, § 5.4.1.1.