Signage

Answer. Subject to the caveat that I am not a First Amendment lawyer, here are my thoughts:

The First Amendment to the U.S. Constitution provides:

The Manual on Uniform Traffic Control Devices (MUTCD) issued by the U.S. Department of Transportation and the Federal Highway Administration specifies the standards for all traffic signs. On both public streets and private property streets on which the public has access, signs must adhere to these standards.