Well if the government can take away your right to fly on an airplane I don’t see why it can’t take away your gun. The no fly list is as much an abridgment of your civil rights as anything is. Personally I don’t have a problem with denying a gun to people on the no fly list. The real issue is whether the no fly list itself is unconstitutional.
And... anywhere close to being accurate, sufficient, complete, workable, defeatable, etc.