Without facts.......
We don't know.
But we DO know there was a massacre in Fallujah, and that reporter may have very bad incriminating evidence of the heavy handedness of our troops, and rather than allow those photos and information to leak to the press, it's much easier to lump him in with the terrorists and give him a military tribunal.
I'll bet they've already confiscated his vidence and are using him as a scapegoat for other reporters who'd do the same.