Allowing the government to deny a right (or privilege for that matter, due process isn't limited to constitutional rights) by its own decree by placing someone on a watch list without providing notice of the deprivation to the individual and an opportunity for the individual to contest the decision runs contrary to the most basic principles of due process (i.e., notice and an opportunity to be heard). This isn't just about gun rights, even if right now that's what the focus is on. It would set a horrible precedent that could be used for the government / law-enforcement to deny, seize, deprive citizens of rights, liberties, property, privileges through executive action alone without judicial oversight. We all remember checks and balances from eighth grade civics class. This would eliminate the judicial check that is supposed to protect individuals from erroneous deprivations--guns or otherwise.
