Both Jack Goldsmith and Harold Koh have recently written about the constitutionality of congressional restrictions on the transfer of prisoners. The President’s veto last week of the NDAA was based in part on his objection to the restrictions it places on such transfers. Those restrictions could prevent the president from fulfilling the promise he made at the beginning of his presidency to close Guantanamo.
One argument cited in favor of congressional restrictions on prisoner transfers is the Constitution’s language giving Congress, not the president, the power to “make Rules concerning Captures on Land and Water.” As Jack points out, a January 2009 Office of Legal Counsel Memorandum argues that the Captures Clause gives Congress the power to determine rules governing the capture and treatment of prisoners. This OLC Memorandum cites practice from the Revolutionary War and from early 19th Century sources which use the term “capture” in connection with people, as well as the 1814 case, Brown v. U.S., a property case which also briefly discusses prisoners.
I disagree with this interpretation of the Captures Clause. The Continental Congress did sometimes use the term “capture” to refer to people during the Revolutionary War, as in a 1781 discussion of issues “relating to Mr. Laurens’s capture” and a 1779 reference to “prisoners  captured by the Continental vessels of war.” Capture was much more often used, however, to refer to act of taking a thing, or to a prize (also property). Moreover, the term “captures” (with an “s”) was less common and apparently not used to refer to people. As well, the language of the Articles of Confederation from which the Constitution’s Capture Clause was taken did not extend to people. That language referred in part to “rules for deciding in all cases, what captures on land or water shall be legal,” and a “lawful” or “legal” capture was used in reference to property, not people. As for Brown v. U.S., its discussion of captures with respect to people is dicta.
Congress did pass early legislation governing the treatment of prisoners and it sometimes used the terms "capture" or "captured" in reference to people. Legislation from February 1799, for example, gave the president the power to “exchange or send away” French prisoners taken from captured vessels. And in March of 1799, Congress directed the president to “cause the most rigorous retaliation to be executed” on captured citizens of the French Republic. Members of Congress themselves viewed the source of Congress’s 1799 power as perhaps the Marque and Reprisals Clause or the Declare War Clause (because these measures risked provoking a full scale war). Or congressional power over the general treatment and taking of prisoners might instead come from its power to make “Rules for the Government and Regulations of the Armed Forces,” a possibility discussed by Mike Ramsey here. And maybe a politically weak President Adams in 1799 simply wanted Congress to authorize his each and every move in the undeclared naval conflict with France. In any event, although the evidence is not entirely one-sided, I think the Captures Clause is best read to apply to property but not to people.