This afternoon, members of the Senate Foreign Relations Committee will have an opportunity to demonstrate why the Framers gave the Senate the constitutional power to confirm presidential appointees. If they fail to exercise that power vigorously with respect to the nomination of Harold Koh to be the top State Department lawyer, they will not only have been derelict. They will be accomplices to an assault on our Constitution that ultimately will result in an unprecedented, and likely permanent, derogation of the Senate's vital role and responsibilities. After all, Mr. Koh is one of the nation's most prominent - and aggressive...