This page originally reproduced a long excerpt from an ACLU guide. Rather than treat old legal text as a current, universal rule, use the ACLU’s photographers’ rights page for its present U.S. guidance and related resources.
The ACLU describes constitutional protection for photographing things plainly visible from public spaces, including officials carrying out public duties. That does not give a photographer permission to trespass, interfere with an operation or ignore rules that apply on private property. State and local rules and the facts of an encounter can matter. This is a general pointer, not legal advice; seek qualified local advice for a specific situation.
The animated video below was made with the ACLU’s photographers’ rights resource by HitRecord, with music by the Gregory Brothers and direction by Joseph Gordon-Levitt.