Sheriffs do not have to enforce federal law, but they do not have the authority to arrest federal agents for enforcing federal law.
They most certainly can arrest on any reasonable probable cause raised by a citizen.
The issue of enforcing law can be adjudicated, subject to discovery.
Actions by federal agents UNDER COLOR OF LAW are not immune to sheriffs arrest.
Ultimately, the courts will decide if arrest was proper, and that will occur after both sides have said their piece.
They the authority if they have over whelming force.
“Sheriffs do not have to enforce federal law, but they do not have the authority to arrest federal agents for enforcing federal law.”
You’re half right. If the feds are enforcing federal law, sheriff’s cannot interfere. If the feds are enforcing illegal diktats and harming citizens, the feds can be designated as terrorists under a state’s anti-Klan law and arrested.
Then we get into a pissing contest over the issues of sovereignty and qualified immunity.
The real problem for the feds is that they don’t want to get their hands dirty and rely on assistance from state and local authorities to carry out federal operations. If the state refuses to help, that means the feds have zero assistance or back-up in carrying out any operation.