Supreme Court Vacates Fourth Circuit Al-Marri Case and Remands With Order To Dismiss:
Seems like the right move to me, and certainly not unexpected. Via SCOTUSblog, here is the order:
The application of the Acting Solicitor General respecting the custody and transfer of petitioner, seeking to release petitioner from military custody and transfer him to the custody of the Attorney General, presented to The Chief Justice and by him referred to the Court is granted. The judgment is vacated and the case is remanded to the United States Court of Appeals for the Fourth Circuit with instructions to dismiss the appeal as moot. See United States v. Munsingwear, Inc., 340 U.S. 36 (1950).
This means is that the 4th Circuit's splintered opinion in Al-Marri will be wiped off the books, and if the issue ever comes up again there won't be any controlling precedent either way.