An inconvenient truth, to be sure, but everyone is entitled to the same rights, and in particular, even the nastiest scum-suckingest dirtbags this side of the Khyber Pass.
I know it doesn't sound right, but that's the bottom line. We don't get to choose, on the basis of sympathetic and emotional reasons, who is entitled to avail themselves of their rights under the Constitution. That's because those rights are, in the words of the Founding Fathers, "endowed by their Creator." [see: The Declaration of Independence; Fifth & Sixth Amendment to the Bill of Rights, etc.]
Yeah, I know, it doesn't sound fair. But if the government can, sua sponte, decide who is entitled and not entitled, then they aren't really rights, are they? More like privileges bestowed upon children who do their homework before supper.
So, even when such scum-sucking dirthbags like Khalid Sheikh Mohammed are, after criminal investigations by foreign countries, captured by foreign services in a non-war zone, and turned over to the United States for interrogation and trial in connection with their various crimes, then at that point he is entitled to a fair trial under our Constitution. That's the breaks.
That's our Constitution and those are our laws. If you don't like it, then go live in another country.