Rand Paul's filibuster has everyone talking about domestic drone strikes. This is a good thing, because domestic drone strikes would be A Very Bad Thing. On the other hand, there are a fair number of conservatives who assert that Rand is wrong that the US Government should not be able to specifically target any US Citizen on US Soil. They claim that if someone has "taken up arms against the US" they do not deserve Constitutional protections.
This is a highly dangerous position. I'll even go further. The US does not have the right to assassinate anyone on US soil- citizen or otherwise. Let's break it down a little bit.
First off, they assert that targeting a US Citizen "who has taken up arms against the US" is the same as targeting That Guy (I'm not even going to try to spell his name) in Yemen. They assert that if the US can do that, they should be able to do it here on US Soil. "If you've taken up arms against the US Government, you've renounced your citizenship!" they say. "The US didn't provide Due Process to Confederate Soldiers in the Civil War!" they say. So let's take apart this argument to see if it holds up.
As I see it, this part of their argument is based on three false assumptions. First, that targeting someone overseas is the same as targeting them here. Second, that "taking up arms against the government" is some legal standard for revoking citizenship. Third, that swearing allegiance to an organization is the same as swearing allegiance to another government.
As to the first: When someone has removed themselves from the effective reach of Justice, Justice must still sometimes be served. It is not impossible that the only reasonably available option to end the threat someone on foreign soil represents is an assassination (no: I'm not using the term "targeted killing." Words have meaning). For That Guy in Yemen, I'm satisfied that this was the case. Yemen is not exactly a cooperative government, so military strike was really our only option. We could have put our boys in harm's way, or we could hit him with a drone strike. I'll take "drone strike" in any case.
However, when someone is on US Soil, there are no foreign impediments to civil justice. We can arrest people here where it is neither practical nor wise to do so on a battle-field or in a non-cooperative (let alone hostile) country. An attempt to capture someone may end in their death- this happens with normal arrests often enough that it sometimes doesn't even make very much news. However, even in those cases, if someone had surrendered, they would have been taken into custody.
The second false assumption: taking up arms automatically revokes your citizenship. Did taking up arms against the US Government revoke the citizenships of Tim McVeigh, Bill Aries, or Bernadine Dorn? No. Nor should it. Indeed, the US specifically treats people who take up arms against the government as citizens. You cannot "rebel" against a government of which you are not a citizen.
These errant conservatives, however follow that up and say: "Well, no, not everyone who takes up arms against the government has revoked their citizenship, but swearing allegiance to a foreign power is what does it." That brings us to the last false assumption.
This false argument is most often framed in terms of the civil war. Confederate Soldiers, it is asserted, were not given due process rights. Therefore someone taking up with Al Qaeda or other terror groups should not count as citizens. There are lots of problems with that argument; I'm going to hit a couple briefly.
First, Confederate Soldiers taken on the field of battle were a) taken on the field of battle and b) treated as POWs. Confederate spies in Union Territory (when caught) were not given most due process rights- that's true. What is overlooked there is the official declaration of emergency that President Lincoln had issued, the fact Martial Law had been invoked (meaning no one actually had due process rights), and that President Lincoln had suspended Habeus Corpus.
Second, being a Confederate Soldier was much more like (indeed, it specifically was) officially revoking your US Citizenship and becoming a citizen of another nation. This would be like defecting to Russia, China, or Iran. "Swearing Allegiance" to an organization is completely different. It's much more like joining the Mob or even the IRA. Neither of these are governments. Neither of them can provide rights of citizenship, or any other function a government provides. Simply joining a group which has taken up arms against various governments does not revoke your citizenship.
This is enough to make that first argument moot. When talking about domestic terror, we are not talking about terrorists on the battlefield. We are not even talking about terrorist sympathizers/agitators who have removed themselves from the reach of our justice system. We are talking about people well within the reach of our civil justice system. Therefore the first duty is to capture them. Again, that is not always possible, but death while resisting arrest is far different from being assassinated.
Now, even setting all of that aside- what is the legal standard for revoking someone's Due Process rights? Is there any? That was another part of Senator Rand's question. If there is a legal standard, who has that authority?
Some would say "the moment" someone takes up arms they've revoked their own citizenship. Again, that is a dangerous standard. Who defines "taking up arms against the government?" I'm going to guess "the government." That's not good.
I would argue that, as long as they are on US Soil, there is no reason to take away someone's Due Process. Now, exactly what form that "due process" takes may vary. I have no problem with someone suspected of actual terrorism (say: planting a bomb, wanting to release poison gas, etc.) with being handed over to the military for a military tribunal. But that is a specific form of due process.
After this wall of text, it's really fairly simple- when there are no unreasonable impediments to the justice system, you get due process. That means no assassination. When there are unreasonable impediments to the justice system, you do not get due process. Due process is a function of justice; if you have removed yourself from the reach of justice, you do not then get any of its benefits.