I partially agree with Levant. And that means I also disagree with Justice Scalia. In Heller Mr. Scalia wrote that the RKBA is subject to "reasonable" regulation. I disagree with this, and the basis is the Bill of Rights itself. There is nothing in the 2nd Amendment to suggest, even in the most indirect fashion, that the RKBA might be subject to even the most reasonable of regulations. Regulation = infringement, and the operative clause of the 2A is an absolute, complete, total prohibition against infringement (i.e. regulation) of the RKBA.
USSC has already addressed that at least somewhat in the 1936 Miller
decision -- military weapons are the MOST protected and subject to the least restrictions, not the most restriction. That is what the prefatory clause is all about.