Not if he appoints a judge that bans you first. Which is possible, depending on your government type, I believe.
But then you need a judge that also wants to destroy the realm. Underground membership is secret so he has to ban everyone. It takes three days for the ban to take effect, which potentially gives you enough time to lead a successful rebellion.
On top of that if your realm has multiple duchies dukes can secede and regions can change loyalty to the new realm. Then that realm can declare war on the original, oust the mad king and his judge and rename the realm back to its original name.
