Life hack: Don't like police, think they are #ACAB... easy solution. You can tresspass anyone, including police. Use a FOIA request, get the list of all police for your district, and issue a tresspass warning preemtively for all of them.
Now if they step foot on your property (without a warrant) it is a criminal and arrestable offense. Obviously they can still come on your land in an emergency without a warrant (exigent circumstances it is called). But if they try to violate your rights, you have a much stronger case to have them jailed.
@miyagiyoda Depends largely on the location. In some states as far as my limited knowledge goes a no trespassing sign might be sufficient if they dont have a warrant or exigent circumstances. I know in PA it is supposed to be.
Problem is a cop can easily lie and say there was no sign (and perhaps rip it down even). A written formal notice is a little harder to talk their way out of.