IMO this is just a bunch of scare talk. BHO does not have the authority to institute gun registration which is what this would be. It would create such a backlash from the public that States would just nullify it and Congress would be forced to act. Most people would not even bother to do it. If they pushed the issue it might even set off CWII.
More likely Barry will just pump up the rhetoric and let Feinstein introduce her gun control legislation for the umpteenth time where it will get buried in committee as usual. Its a win win for Barry.
There already are illegal gun registrations. NICS was specifically banned from keeping records, yet, after years of Janet Reno she kept it.