Or the government could try to persuade a judge that any confession by Mr. Tsarnaev resulting from such an interrogation could be used as evidence against him under the "public safety" exception to the Miranda rule.
Critics of the Bush administration's interrogation programme say the memos provide evidence that many of the methods amount to torture under US and international law.
Under the new procedure, they appear to have retained their powers to arrest suspects, who, after interrogation, will then presumably be handed over to the military courts.