I'll let Ian Welsh take it from here. Welsh says Paul took this action "in order to get clarification from the President that American citizens can’t be killed without due process in the United States." and then continues:
I’m seeing a lot of “liberals” and “progressives” attacking Rand Paul. Be clear, Rand Paul is a bad man. But he is doing the right thing right now, and if you are attacking him at this moment, you are scum. Also, be clear, that in terms of actual evil committed Rand Paul is not as evil as Barack Obama. For one, he has not killed nearly as many children as Barack Obama. He has not gone to war in violation of the constitution, as Obama has. Perhaps, if given a chance, Rand Paul would be more evil than Barack Obama, but he is not more evil yet.
The right to a trial, in which you see the evidence against you and have the right to face your accusers (and don’t have evidence gained through torture) is one of the main reasons the American Revolution was fought. Barack Obama and George Bush have destroyed America. Something shambles on bearing the name, but the Bill of Rights is near dead and you have an elected dictator who arrogates to himself the right to kill anyone any time he wants. He arrogates to himself the right of Kings.
So yeah, Rand Paul’s a bad man. But he’s doing the right thing. And I notice it isn’t, say, Bernie Sanders, “socialist” who is standing up for the right of Americans not to be killed out of hand by their own President. Only one Democrat, Ron Wyden, has joined Paul.
The American Republic died when the Patriot Act and the AUMF were passed. More acccurately perhaps, it died on 9/11, when Americans decided to throw aside the Republic they had been given, trying to give up a little liberty for a little safety (and getting neither). The Republic had been shambling along, half dead for some time, mind you, but that was the end of it. You still have elections, sure, but the President is Emperor and you are his subjects. The real constituents are the very rich, and corporations, as was codified in Citizens United.
When Augustus took over, he became “first citizen”. He kept the Senate around. He just took away all their meaningful power.
So it goes.