32 C.F.R. § 501.5 Protection of Federal property.
Title 32 - National Defense
The right of the United States to protect Federal property or functions by intervention with Federal Armed Forces is an accepted principle of our Government. This form of intervention is warranted only where the need for protection exists and the local civil authorities cannot or will not give adequate protection. This right is exercised by executive authority and extends to all Federal property and functions.
Title 32: National Defense
PART 501—EMPLOYMENT OF TROOPS IN AID OF CIVIL AUTHORITIES
§ 501.5 Protection of Federal property.

