I'm going to have to figure out a way to deal with this in-law and set clear boundaries, but being that I'm sort of on the periphery of family, I've got to find a way to start putting roadblocks up and make sure this doesn't happen again without playing the "choose between me or your blood kin
DumbLiberalVet: If, as you say, your husband's nephew is moving in with you, got news for you. You ARE NOT on the periphery of anything, and you'd better keep all your valuables under lock and key. As for your hubby, he's not only enabling his sister and her son, but his parents as well. You should have stayed 2000 miles away.
Someone has to be the first to say loud and clear NO ****ING WAY. Get the nephew to a halfway house or something. And don't worry, odds are he'll be in jail before too long anyway.
There you go, free advice.