This is the problem with all party based content, but I believe there was a post a week or so ago that said if rules are agreed upon in chat and someone breaks those rules you can contact a GM and the item will be confiscated.

Obviously you will need to prove that the person in question agreed upon the rules before the item was rolled upon.

It is a pain, but people will be people and there are a lot of greedy ones about.

Loot master options would be nice but these can also be abused.