He thought he thought he could get away with that because it was his last semester and he had been accepted into the masters program at Stanford. We talked to the professor and the professor kicked him out of the class.
If someone isn't carrying their weight in college, you rat them out to the professor. If the professor won't do anything, you go to the department head. It's not high school. You don't have to try be cool anymore. You're there to learn skills for your life, not worry about whether or not the thump dick that isn't doing the work will like you or not.
Either you design the assignment so that each person is responsible for a different segment of it, and then they bring it together at the end, or you require each group member to provide some kind of nontrivial write-up of their own contributions, and what they learned, as part of it.
Ultimately, the key is never to grade individuals in the group based on anyone's performance but their own. Otherwise it's just another form of collective punishment, which is pretty damn unethical.