What exactly did Attorney General Eric Holder mean when he said, in response to questions from Rand Paul (R-Ky.) and other senators, that he could envision "extraordinary circumstances" in which it would be "necessary and appropriate" to use lethal force on U.S. soil against Americans suspected of involvement in terrorism? Given a chance to clarify his position during his testimony before the Senate Judiciary Committee today, Holder resisted mightily.

In his March 4 letter to Paul, Holder said "the president could conceivably have no choice but to authorize the military to use such force if necessary to protect the homeland in circumstances like a catastrophic attack like the ones suffered on December 7, 1941, and September 11, 2001." This morning Holder elaborated on the latter scenario, citing President Bush's consideration of authorizing the Air Force to shoot down United Flight 93, the airplane that crashed in Pennsylvania on the way to Washington, D.C., after passengers fought back against Al Qaeda hijackers. But the moral and legal issue in that case was whether the lives of innocent passengers (who almost certainly would have died anyway) should be sacrificed to save potential victims at the White House or the Capitol. There was no question that using lethal force against the terrorists themselves, who posed a clear and imminent threat, was justified as an act of self-defense.

In any case, as The Atlantic's Conor Friedersdorf notes, Holder's letter suggests he did not have in mind the use of force against terrorists in the midst of an attack. "Were such an emergency to arise," Holder wrote, "I would examine the particular facts and circumstances before advising the president on the scope of his authority." If Holder imagines he will have time to draw up a memo, he clearly is not talking about a threat like a plane that is about to crash into the Capitol. At today's hearing, Sen. Ted Cruz (R-Texas) repeatedly pressed Holder to say whether it would be constitutional to kill a suspected terrorist on U.S. soil if he did not pose an immediate threat. Holder dodged the question again and again, allowing only that killing a suspected terrorist who was just "walking down a path" or "sitting in a café" (as in Cruz's hypothetical) would not be "appropriate." Cruz complained:

You keep saying "appropriate." My question is not about propriety. My question is about whether something is constitutional or not….Do you have a legal judgment as to whether it would be constitutional to kill a U.S. citizen on U.S. soil in those circumstances?

Finally, after Cruz had given up on getting a straight answer from him, Holder said, "Translate my 'appropriate' to no. I thought I was saying no." No, he does not have an opinion, or no, he does not think it would be constitutional? Going with the latter interpretation, Cruz wondered why Holder resorted to rhetorical "gymnastics" instead of giving a direct answer and why he did not say as much in his letter to Paul.

The difference between inappropriate and unconstitutional is no small distinction, as the language Holder used in his letter suggests:

As a policy matter…we reject the use of military force where well-established law enforcement authorities in this country provide the best means for incapacitating a terrorist threat. We have a long history of using the criminal justice system to incapacitate individuals located in our country who pose a threat to the United States and its interests abroad. Hundreds of individuals have been arrested and convicted of terrorism-related offenses in our federal courts.

Holder says "as a policy matter" so as not to commit himself on the question of whether this approach to terrorists located within the United States, which the administration currently considers "appropriate," is legally required. Likewise with his maddeningly evasive remarks today, in which he resisted taking a clear position on the question of whether the license to kill claimed by the president includes the authority to order a hit on American soil.

You can watch the hearing here. The exchange with Cruz starts around the 1:19 mark.