I never did catch what part of the Constitution you claim covers individual ownership of guns, since it seemed your were arguing the other day that A2 was specifically about militia.
The same part of the Constitution that protects other natural rights, such as the right to privacy. That natural right, btw, is the right to defense of home and property. Facially, the 2A doesn't address the natural right; it's about the citizens' militia. Heller confirms that the RKBA for purposes of individual self defense is protected by the Constitution. Just as the right to abortion (derivative of the right of privacy) is. You can't be denied your right to own guns to protect your home, but that has nothing to do with whether the peoples' elected representatives can decide to require for reasons of public safety that you register your guns (or, in the case of abortion, to require the dirty deed be done prior to the 20th week of pregnancy). Registration isn't denial of the right. Nor does reasonable regulation constitute denial of the abortion right.
All rights are not absolute, and can be regulated as to time, place and manner of exercise. Heller confirms as much with respect to the gun right.