It's a setup and betrayal - Sheriff Joe has thrown in with the drug runners and illegals. He's having his troops dress and act like the enemy in order to provoke the civilian militia into responding, and then reveal that they are cops and arrest the militia.
Sabotage. Betrayal of law abiding Americans. It's a sting operation to help the illegals, because now the militia doesn't know if the illegals are cops setting them up.
What are the militia doing that is illegal?