Jack Goldsmith headed the White House's ultra-secret legal arm, the Office of Legal Counsel, and his attempts to rein in the "unitary executive" infuriated David Addington. So what's his advice for Barack Obama and Congress on investigating those same excesses? Don't bother. A congressional or Justice Department investigation "would bring little benefit, and they would further weaken the Justice Department and the CIA in ways that would compromise our security." The relevant facts, he says, are "well known inside the government," and several investigations, both public and private, have already been conducted. Obama should allow these investigations to continue and make their findings public. But new investigations could spook intelligence agencies from properly doing their jobs. "The greater danger now," Goldsmith writes, "is that lawyers will become excessively cautious in giving advice and will substitute predictions of political palatability for careful legal judgment."