36 CFR § 2.31 - Trespassing, tampering and vandalism.
(a) The following are prohibited:
(1) Trespassing. Trespassing, entering or remaining in or upon property or real property not open to the public, except with the express invitation or consent of the person having lawful control of the property or real property.
(2) Tampering. Tampering or attempting to tamper with property or real property, or moving, manipulating or setting in motion any of the parts thereof, except when such property is under one's lawful control or possession.
(3) Vandalism. Destroying, injuring, defacing, or damaging property or real property.
(4) Harassment. Intentional or reckless harassment of park visitors with physical contact.
(5) Obstruction. Intentional or reckless obstruction of any sidewalk, trail, highway, building entranceway, railroad track, or public utility right-of-way, or other public passage, whether alone or with others. The mere gathering of persons to hear a speaker communicate, or simply being a member of such a gathering, does not constitute obstruction. An official may make a reasonable request or order that one or more persons move in order to prevent obstruction of a public passage, and refusal of such an order constitutes obstruction.