I view this as more of a 4th Amendment issue, unlawful seizure of property (retaining the property). I suppose that if the plaintiffs could show a pattern of such behavior, it might implicate the 2nd Amendment, but that's probably a more difficult case to prove.
Jim's Rules of Carry: 1. Any gun is better than no gun. 2. A gun that is reliable is better than a gun that is not. 3. A hole in the right place is better than a hole in the wrong place. 4. A bigger hole is a better hole.