Well, it's deeper than it seems. You cannot just start revoking random people's citizenship for being relatives of the loosely defined bad guys. That's the straight route to turning your own country into a 3rd-world dictatorship.

What you can do is tighten the anti-money-laundring laws, so that living in the West off money made in sketchy ways becomes harder, but there's a major conflict of interest here. A lot of the West's wealth is fueled by the dirty money flows from elsewhere, and cutting it off without inevitable side effects (e.g. real estate crash) is not an easy task.