This post by Ryan McMaken conveys my view on this subject better than anything I can write. So I won’t write, and instead thank Mr. McMaken for this.
Update: The filibuster ended based on the following assurance from Attorney General Eric Holder:
Mr. Holder made his point in a letter to Mr. Paul, in which he wrote: "Does the president have the authority to use a weaponized drone to kill an American not engaged in combat on American soil? The answer is no."
Of course, it is a statement that a president can drive a truck through. But it doesn’t change my earlier view, as so well expressed in the post by Mr. McMaken.