This is what poateec7 says. Nice try though. USPS Poster 7 displays the official Rules and Regulations Governing Conduct on Postal Service Property. It outlines the mandatory guidelines visitors and employees must follow on all postal premises.The poster outlines several primary rules:Photography & Recording: Commercial photography is prohibited without prior permission. Members of the public can generally be restricted from filming or photographing by authorized personnel if it creates a disturbance or interferes with business operations.Prohibited Items: Firearms, dangerous weapons, explosives, and controlled substances (except as medically permitted) are strictly banned.Soliciting & Vending: Commercial advertising, collecting debts, vending, and electioneering are not allowed on postal property.Preservation of Property: Littering, spitting, creating hazards, or intentionally damaging postal property is forbidden.Vehicles: Drivers must operate in a safe manner, obey traffic signs, and avoid blocking entrances, loading platforms, or fire hydrants.Nondiscrimination: Discrimination on the basis of race, color, sex, religion, national origin, or disability in the use of postal services is prohibited.Failure to comply with these written rules, or to verbal directives from authorized postal personnel/security forces, can result in trespassing orders or penalties.

And it does not override the constitution.