The 12-page decision, by a per curiam panel composed of Judges Henderson, Tatel, and Griffith, is here. The decision includes this paragraph:
The Members [of Congress] can, and likely will, continue to use their weighty voices to make their case to the American people, their colleagues in the Congress and the President himself, all of whom are free to engage that argument as they see fit. But we will not—indeed we cannot—participate in this debate. The Constitution permits the Judiciary to speak only in the context of an Article III case or controversy and this lawsuit presents neither.