In Hamdan v. Rumsfeld, the Supreme Court reversed (5 to 3) a decision that John Roberts had joined when he was on the D.C. Circuit. Hamdan held, first, that it had jurisdiction. In other words, the Detainee Treatment Act of 2005, which limited federal jurisdiction, did not apply to pending cases. Second, the Court held that the Uniform Code of Military Justice did not authorize the President to set up “military commissions” (or “war crimes tribunals” in popular parlance) to try alleged war criminals....