Posse comitatus

Posse comitatus was an American federal statute prohibiting the deployment of Army or Air Force units on American soil. However, the United States Marine Corps and the Navy were not subject to this restriction.

On Day 2, President David Palmer ordered Mike Novick to place a call to General Bowden regarding using the Army to quell riots on the East Coast in the wake of the nuclear detonation in California. Novick reminded him of the statute, but agreed to call the general upon Palmer's insistence.

Several years later, on Day 5, Vice President Hal Gardner instituted martial law by the Army in the city of Los Angeles to help track down Vladimir Bierko, effectively overturning posse comitatus for the duration of the crisis.