Kevin D. Williamson explains to National Review Online readers this morning the importance of Kentucky Sen. Rand Paul’s filibuster of the nomination for a new CIA leader.

Senator Paul’s decision to stand in the way of this appointment is not about persons but about policy – specifically, the Obama administration’s claim that it has a legal and ethical mandate to carry out extrajudicial killings of American citizens overseas that are indistinguishable from assassinations, and, especially, the administration’s recent terrifying expansion of that policy to include the option of putting to death Americans in the United States without trial, proper legal process, or meaningful oversight. Given that the CIA has been the instrument entrusted with carrying out these killings in several cases already, holding up Mr. Brennan’s appointment is appropriate. …

… There is no question that killing an American citizen under arms in the course of battlefield combat is easily within the bounds of acceptable national-defense action.

But that is not the question before us. Instead, we are faced with an arrangement by which the president may designate any American, at home or abroad, as an “enemy combatant,” and place him on a list of people to be killed — not in the course of combat, but in targeted operations indistinguishable from assassinations. The legal justification for this is derived from the penumbras of the 2006 Military Commissions Act — but Congress has passed no law specifically authorizing the premeditated, targeted killings of American citizens abroad, to say nothing of American citizens at home. I very much doubt that such a law could pass Congress, even as defective and unreliable as our Congress can be. Passing such a law would not make these killings any less problematic, but it would introduce a much-needed balance-of-powers element to the situation.