On Wednesday, I rose to begin a filibuster on the nomination of John O. Brennan to be director of the CIA. I stood up with the intent of speaking until I was no longer able to speak. I vowed to speak as long as it took, until an alarm was sounded from coast to coast that our Constitution is important, that our rights to trial by jury are precious, and that no American should be killed by a drone on US soil without having been found guilty in a court of law.

I didn't rise to oppose Mr. Brennan's nomination simply based on him as a person. I rose to defend the principles of our Constitution, principles for which we have fought long and hard. To give up on that principle -- the Bill of Rights, the Fifth Amendment -- is a travesty. I will not sit back and allow the president to shred our Constitution.

When I asked the president, "Can you kill an American on American soil?" it should have been an easy answer. It should have been a resounding and unequivocal, "no." But what was the president's response?

For his first response, the president said, "I haven't killed anyone yet, and I have no intention of killing Americans. But I might." Were we supposed to be comforted by this? Had we become so complacent with our rights that we would allow a president to say he might kill Americans?

James Madison said restraint on government is necessary because government will not always be run by angels. This has absolutely nothing to do with whether the president is a Democrat or a Republican. Were this a Republican president, I'd be saying exactly the same thing. No one person, no one politician should be allowed to judge the guilt of an individual and to execute that individual. It goes against everything that we fundamentally believe in our country.

Now, some of my colleagues might take to the Senate floor and say, "Well, what if we're being attacked on 9/11? What if there are planes flying at the twin towers?" To that, I firmly say, by all means, use lethal force. You don't get due process if you're involved in actively attacking us, our troops or our government. You don't get due process if you're overseas in a battle shooting at our soldiers. But that's not what we are talking about here. We are talking about noncombatants.

On Thursday, I finally received an adequate response. Attorney General Eric H. Holder Jr. wrote: "It has come to my attention that you have now asked an additional question: 'Does the President have the authority to use a weaponized drone to kill an American not engaged in combat on American soil?' The answer to that question is no."

"No" was the acceptable response. No, the president can't assassinate Americans sitting in cafes; no, he can't kill you at home in your bed at night; no, he can't drop bombs on restaurants.

Friedrich A. Hayek said that nothing distinguishes arbitrary government from a government that is run by the whims of the people more clearly than the rule of law. The law is an amazingly important thing and our main form of protection. To let this issue slip under the radar would be an insult to our Founding Fathers and an insult to what generation after generation of American troops have fought for, and what troops are fighting for today when they go overseas.

When the president took the oath of office, he vowed that he would, to the best of his ability, preserve, protect and defend the Constitution. He raised his hand, his right hand, put his left hand on the Bible and said, "I will." What the president doesn't say is, "I intend to if it's convenient. I intend to, unless circumstances dictate otherwise."

When Mr. Brennan was asked directly, "Is there any limit to your killing? Is there any geographic limitation to your drone strike program?" He responded no, there is no limitation. The obvious question would be, then, if there's no limitation to whom you can kill and where you can kill and there's no due process, does that mean you will do it in America?

We have separation of powers to protect our rights. That's what government was organized to do, and that's what the Constitution was put into place to do.

I think this is something we shouldn't give up on so easily. The president does not have the power to act as the judge, jury and executioner. Are we so afraid of terrorism that we're willing to just throw out our rights and our freedoms?

Montesquieu said there can be no liberty when you combine the executive and the legislative. I would say that there can be no liberty when you combine the executive and the judiciary, yet that's what we would be doing here. No man should have that power. It has nothing to do with whether you're a Republican or Democrat. It has to do with whether or not you fear the consolidation of power.

This is what our Founding Fathers wanted to fight. They wanted to limit the role and the power of the president. They wanted to check the president's power with the power of the Senate, House and judiciary. Wednesday night, I stood proudly with bipartisan senators declaring that we will not tolerate this. We all came together to tell the president, to tell any president, that no one will ever have the authority to kill Americans without a trial.

I am glad to have finally received an answer from the White House. I will always fight for American civil liberties by any means within my power as a United States senator.

This article was originally published in The Washington Times. Refer to original article for related links and important documentation.