This is the case formerly known as Parker v DC. DC appealed to SCOTUS so they are now listed first (Plaintiff in error/appellant) while Heller is listed 2nd. Heller is the only original plaintiff with standing, so his name goes on there first.
From SCOTUS BLOG - DC files their brief against Dick Heller
It's a PDF file.
Also related to the case. The former DC attorney arguing the case, Alan B Morrison (Of advocacy group Public Citizen) was fired. Walter Dellinger, former acting solicitor general for two years under Bill Clinton, replaces him. Both are experience attorneys practicing before SCOTUS.
I have not read the file yet in depth. It's 79 pages.
The attorneys for Hellerhave their own blog site here. along with all the public documents so far related to the case posted on their site.