UK spooks forced to hand Gitmo files to suspect's lawyers
Dirty bombs, dirty hands for MI5
All in all, it looks quite plausible that Binyam Mohamed may have trained to fight US forces and their allies in Afghanistan and Pakistan, and may have seen combat in that theatre. But plenty of us have done that in the past - even us Brits have fought American forces (and more successfully, American allies) if you go back far enough. Americans have seldom found it necessary until lately to disappear people for years - and then possibly torture and finally execute them - just for taking on Uncle Sam.
Prevention of terrorist attacks on home soil is, of course, a vital objective of all spooks. But a "dirty bomb" attack - even if it were for real - seems like flimsy justification for the measures used here. After all, according to the US nuclear regulatory commission:
"A dirty bomb is in no way similar to a nuclear weapon or nuclear bomb... A dirty bomb is not a Weapon of Mass Destruction... Most [dirty bombs] would not release enough radiation to kill people or cause severe illness... health effects from exposure to the low radiation levels expected from a [dirty bomb] would likely be minimal."
In other words, Mohamed couldn't possibly ever have been any more dangerous to America than, say, a drunk at the wheel of an 18-wheeler. There's every reason to see him as an irritating, untruthful petty criminal as well as a possible irregular serviceman of the pre-2001 Taliban government in Afghanistan - but not in any way as the mastermind of another 9/11.
Even if you agree with the idea that we now have "terrorists", who aren't enemy soldiers and aren't criminals either - and therefore have only Guantánamo rights, or none at all - this is feeble stuff. Even the most fervent War on Terror supporter, the strongest backer of recent US/UK invasions, might agree with the Foreign Secretary and the British spooks that the best move by America at this point would be to send Binyam Mohamed back to Blighty for release and hope to goodness the whole thing blows over quickly. There's no possible benefit to America in pushing on with this.
The publicly-available high court ruling can be read in full here. ®
*"Sy" is the official British contraction of "Security". You can see why they didn't fancy "SS". MI5 was never a proper term to use for the Security Service spooks.