There is a footnote in Ashcroft's letter, although I wasn't able to find where in the text it was referenced:
"1Of course, the individual rights view of the Second Amendment dos not prohibit Congress from enacting laws restricting firearms ownership for compelling state interests, ..."
"Compelling state interests" is one of the criteria of "strict scrutiny" if I recall correctly. The problem is that ANY scrutiny opens us up to somebody's judgement that a particular weapon is just too darn dangerous; which is exactly what DC says about handguns.
The application of "strict scrutiny", however, goes beyond just making unsupported claims. The state must prove that the law in question touches as lightly as possible on the protected right. In the case of handguns in DC, it's hard to see how background checks on gun owners is not sufficient, though even that is an infringement. Background checks have been in effect for many years and crime rates have not been greatly affected by them, as far as I know. DC can't make a credible claim that non-criminals become criminals simply because they own a gun.
Yes, but only one of them. For the typc of scrutiny the DoJ says is appropriate for the second amendment, heightened security, it's the *only* one required.