Suppose Joe Blow in Anytown, USA decides he has heard enough anti American ranting from the head of state of country XYZ. Mr Blow goes travels to XYZ, pops a cap in the guy, and escapes back to America. When it is discovered that Joe is responsible, what happens next?
I am sure he is going to jail. He certainly violated the laws of XYZ, probably some international law too, but I’m not sure what United States law. Can he be extradited?
If Joe Blow had an accomplice he could be on the hook for violating 18 U.S.C. 956 (“Conspiracy to kill, kidnap, maim, or injure persons or damage property in a foreign country”). This applies as long as Joe Blow did his conspiring within the jurisdiction of the United States, even if his co-conspirator(s) never set foot in the U.S.–say he’s e-mailing back and forth with them (or sending telegrams).
If he’s just a Lone Gunman who goes over and blows away the President of Ruritania, though, I’m not sure there’s any U.S. law he could be prosecuted under; I suppose it would come down to extradition treaties.
From what I’ve read at those links, and IANAL, if there’s a treaty and the prosecuting country provides the required evidence, then Joe is going to stand trial outside the US for his crimes. If there’s no treaty the Secretary of State makes the decision as to whether Joe goes.
If Joe was a Brit, he would not be extradited from the UK to anywhere he would face the death penalty should he be convicted, except if it is assured that the death penalty is off the table.
I was in Cambodia once, and saw a rather disturbing sign in English depicting an adult holding hands with a little kid, with the slogan like “Molest a child in this country, go to jail in yours.” A believe there was some small print indicating that the US helped pay for the sign, and were on board with the deal. But is that is a special case? I have certainly never molested a child in Cambodia, but I have fired up a big ole J in Amsterdam. What if I shot a man in Rio, just to watch him die? If the US didn’t want to deal with extradition, could they lock me up at home?
It’s a special case: the PROTECT Act of 2003, among other things, makes it illegal for U.S. residents to travel abroad for the purposes of having sex with children (under 16), regardless of whether or not it’s a crime in the country visited. (See Section 105 of the link.)