Castaneda v us.
The little bit of info I could find is that INS agents raided an apartment inhabited by Castaneda in Bighorn Wy.
A lawsuit followed and the sheriff issued a policy that set rules of how federal officers could operate within his county at which time both parties, including lawyers for DOJ agreed to the terms and settled out of court.

I've read of other instances, one where a sherrif barred law enforcement agents from the forestry Dept from operating in his county.

The best route for Virginia now, Is for the sherrif's to start deputizing law abiding gun owners and form county militias. A few already indicated they would do this if/when it would become necessary.