The US AG's brief came in late last night.
As one might expect, it deals heavily with protecting the existing firearms framework of the GCA/922 laws. The plaintiffs lack standing and the laws do not overly burden the RKBA. Should the Court find standing, in the alternative even if the laws implicate the right, they are constitutional and at most, intermediate scrutiny applies.
Where have we heard this tune before?
Quite frankly, under current Interstate Commerce interpretation, this suit will go nowhere.