Even if Caesar demands you worship him as a god? Professing Christians are held under the doctrine of the Higher Authority. Standing against the government "taking away" or "nullifying" an unalienable right seems fall under the auspices of the doctrine. Of course there are a myriad of things in modern America that the idea could apply to, which we choose to ignore. Maybe we truly are too far from Grace to expect protection?
Worshipping Caesar would be immoral. However, not registering a gun if Caesar demanded it? That’s not so morally clear cut to me as Christian.
BTW, I’m only expressing my own thoughts on the matter and not advocating for or against any other position. I’m simply saying it (gun registration or confiscation) would not be a simple issue, clear cut issue for me. It would also be a deadly serious decision of course.