Do you still have a right to trial by Jury if you committed a capital crime like Murder in the USA and are indicted but are not within its borders. And since you are not within the borders of the United States is it OK that the Government assassinates you rather than go through with a messy trial?
Very, very odd "reasoning."
If I commit a crime, murder or otherwise, in the USA but flee to a foreign country, I can indeed be indicted for the crime. However, I believe I would have to be physically returned to the USA to be tried. So I'm not sure what your point might be.
If I wage war on the United States I would expect them to return the favor, particularly if I'm overseas and in a location not amenable to arrest and extradition. This presents obvious problems with definitions and designation, but I find nowhere in the Constitution that a US citizen engaged in warfare on the USA has special privileges requiring him to be arrested and tried, rather than killed in the same way as a non-citizen engaged in the same activities.
IOW, if I'm in Afghanistan shooting at US soldiers, I expect them to respond in exactly the same way as if I'm an Afghan shooting at them.