Yale Law School professor Harold Koh vilified John Yoo for his so-called "torture memos" legally justifying the use of harsh interrogation tactics during. Now, Mr. Koh is justifying President Obama's undeclared war in Libya and the drone strikes that assassinate foreign and American-born terrorists. They also kill innocent women and children.

As it happens, drone strikes and other Obama war decisions can be legally and morally justified. The problem, however, is that they are hard to justify based on the principles Mr. Koh so loudly advanced before he joined the Obama administration. The legal contortions Mr. Koh introduces in his defenses today as much as admit that.

It is eminently possible that a war might look one way from Yale and another way from Foggy Bottom. A public servant facing that reality has two honorable choices. If he found himself embracing authority he had once denounced others for defending, he would apologize to them. If he still believed his original positions, he would resign.