Maybe the idea is to treat him as a Citizen of the World....
Then charge him with violating the standards of THAT...sets a precedent for others who would violate these new standards.....
That got thrown out with the new standard we now have. If Constitutional protections now extend to everyone in the world, the the prohibition against treason contained within that same Constitution should apply as well. Right? Article III makes no mention of one having to be a citizen to be charged with treason.
The rules have been re-written, so I am merely going by this new set of rules. If liberals insist that KSM should have the right to a trial by jury by a US civilian court for crimes that took place outside the US (e.g. conspiracy), then he should also be subject to treason. Of course these same liberals will quickly shift their standard once again arguing that only the 'good' parts of the Constitution should apply, and not the 'bad' parts.