> they have been getting letters from the DOJ office of legal counsel that say it's legal. This effectively immunizes them (the DOJ can't turn around and charge you with a crime, if they advised you beforehand it was not a crime).

This is not true.

OLC opinions are just that: opinions. They are non-binding and non-promissory. They are an important factor in any assessments as a norm, but definitely not dispositive and not legally binding.

The only real barrier is the pardon power, but I'm personally fine at this point with totally breaking the seal, trying and jailing every criminal in the administration(++), and consider the pardon power gone for good. Small price to pay.