Targeting US citizens v. foreign nationals
Whenever this issue is raised, people quite reasonably ask why there should be any difference in the reaction to targeting US citizens as opposed to foreign nationals. As a moral and ethical matter, and as a matter of international law, there is no difference whatsoever. I am every bit as opposed to targeting foreign nationals for due-process-free assassinations as I am US citizens, which is why I have devoted so much time and energy to opposing that policy. I also agree entirely with what Desmond Tutu recently said in response to calls for a special secret "court" to be created to review the targeting of US citizens for assassinations:
"Do the United States and its people really want to tell those of us who live in the rest of the world that our lives are not of the same value as yours? That President Obama can sign off on a decision to kill us with less worry about judicial scrutiny than if the target is an American? Would your Supreme Court really want to tell humankind that we, like the slave Dred Scott in the 19th century, are not as human as you are? I cannot believe it.
"I used to say of apartheid that it dehumanized its perpetrators as much as, if not more than, its victims. Your response as a society to Osama bin Laden and his followers threatens to undermine your moral standards and your humanity."
But the explanation for why the targeting of US citizens receives distinct attention is two-fold: both political and legal. Politically, it is simply easier to induce one's fellow citizens to care about an abusive power if you can persuade them that it will affect them and not merely those Foreign Others. It shouldn't be that way, but the reality of human nature is that it is (recall how civil liberties and privacy concerns catapulted to the top of the news when US citizens generally - not just Muslims - were subjected to new invasive airport searches). So emphasizing that the assassination power extends to US citizens as well as foreign nationals can be an important instrument in battling indifference.
But there's also a legal difference. As the Supreme Court has interpreted it, the US Constitution applies, roughly speaking, to two groups: (1) US citizens no matter where they are in the world, and (2) foreign nationals on US soil or US-controlled land (that's why foreign Guantanamo detainees had to argue that the US had sovereignty over Guantanamo Bay in order to invoke the US Constitution's habeas corpus guarantee against the US government). While international law certainly constraints what the US government may do to foreign nationals outside of land over which the US exercises sovereignty, the US Constitution, at least as the Supreme Court has interpreted it, does not. Moreover - not just for the US but for every nation - there is a unique danger that comes from a government acting repressively against its own citizens: that's what shields those in power from challenge and renders the citizenry pacified and afraid.
The US policy of killing or imprisoning anyone it wants, anywhere in the world, is immoral and wrong in equal measure when applied to US citizens and foreign nationals, on US soil or in Yemen and Pakistan. But application of the power to US citizens on US soil does raise distinct constitutional problems, creates the opportunity to mobilize the citizenry against it, and poses specific political dangers. That's why it is sometimes discussed separately.