The world's minimum win rules should be strong enough to discourage tanking. At least, that's what the intention of the MWR should be. I don't know what they are in Duff Beer. But a multi-season, progressive rule should be sufficient to make tanking a "do at your own risk" option.
That said, the commish should be able to remove a problematic owner IF he can make a case for doing so with ADMIN. Which means documenting the transgressions via a ticket to ADMIN, issuing "warnings" to the violating owner, etc.
We had an issue in Cooperstown many seasons ago in which we had an owner who was tanking, he was first warned by the commish, and then was flat out told that he would not be allowed back the following season, yet he refused to leave at rollover. The rest of the world banded together, and I believe 28 owners (everybody but the commish, the tanker, and two others who apparently couldn't be bothered) had a walkout (we all withdrew from the world) until ADMIN removed the owner in question.
It was a thing of beauty.