Judge Ginsberg seemed skeptical that the registration requirement violates the Constitution. Judge Kavenaugh was interested in Halbrook's argument that the registration provision violates a Congressional restriction on DC which limits its firearms laws to those which are "usual and reasonable." Judge Henderson said nothing, but remember that she dissented in Parker v. DC, which was the name of the Heller case at the DC Circuit. With respect to the so-called assault weapons ban and ban on standard capacity magazines, it appears Judge Kavenaugh is leaning toward the view that as arms in common use, they are protected. Hard to read the other judges.
DC's attorney must have been speaking at 300 words a minute, but to sum it up, his argument is that so-called assault weapons are unusually dangerous and thus not arms under the second amendment, and that the registration requirement is reasonable and not unusally in light of other jurisdictions which require registration.