First, A noble can not drain a countries gold. He is given it by being allowed to keep an estate. If he does not earn his keep, have his estate taken away. If his Lord refuses to do so, your beef is with the wrong person. Get the lord replaced. If the Duke will not do so, there are bigger issues here. I am not sure why a ban was needed at all...
Also, I understand that the estate was indeed taken away long before the ban was issued.
