Even if overthrowing a government is impossible, making the police who enforce unjust laws hesitate before, lets say, rounding up millions of people for deporta

Even if overthrowing a government is impossible, making the police who enforce unjust laws hesitate before, lets say, rounding up millions of people for deportation, that's a good brake. You slow down the bad processes just long enough to survive until the next election, when all the combined reactance against the unjust government can flush it clean. If the police have no fear and don't hesitate enough to prioritize what they enforce, they will stretch a tyrannical law to its conclusion. I see it like this: If your state passes a law allowing ICE agents to come into schools and take kids with little to no justification, and having armed teachers can make them hesitate enough to only invade 3 schools instead of 4, that's a minor success. Just enough of a brake to spare one immigrant family long enough for Trump to be ousted.