Senators Paul and Cruz have suggested that the constitutional claim they’ve posited — viz., presidents are not empowered to kill Americans on American soil absent an imminent threat of violence — is “easy,” “clear,” and “obvious.” I respectfully disagree. It is none of those things. What is easy, clear, and obvious is that if we do not need certain troublesome authorities to fight a war successfully, Congress can withhold them.

Why does it make a difference whether this curtailment comes from the AUMF rather than the Constitution? Because, absent a sudden-attack situation, the Constitution makes Congress the master of what force is lawfully authorized, while our tradition holds that the courts are masters of what the Constitution means.

Since 2004, courts have made themselves a part of the national-security equation to an unprecedented degree. When challenged to construe constitutional doctrines, they seek to impose logic. Senator Paul’s proposal of a Constitution-based no-lethal-force exception to the principle that an American who joins the enemy may be treated like the enemy is not logical…

I do know this: If all the senator really has in mind is some curtailment of presidential overreach, the right way to do that is to limit the AUMF. If his ambition is greater, if he believes the country would be better off ending the war paradigm and returning to peacetime due process, the forthright way to do that is to repeal the AUMF. That would be a terrible mistake, but one we could withstand, however painfully. What we might not be able to withstand is the shackling of constitutional powers we may someday need to sustain the United States.