The letter is here, and it is signed by the Attorney General personally. The contents strike me as unexceptional, as it’s just what the DOJ lawyer said at oral argument and DOJ has been saying in its briefing. As ordered, the letter consists of three pages and is single spaced.
I assume this will satisfy the Fifth Circuit judges, although at this point nothing would surprise me. (I’m sure someone will say that Holder should be arrested because the three page letter has only two pages of actual analysis, but the court’s written order said that the letter should consist of three pages, which this letter does.) Thanks to Tim Sandefur for the link.