The Writ of Habeas Corpus is such a seldom used Writ anymore and has been eroded by decisions of the S.Ct. in the past decade or so to limit its use.  However, it seems from the brief updating I've done on my knowledge of the Writ that Pvt. Bradley Manning's situation would be very appropriate.  This assumes that the facts are at least somewhat as the news and net reports have reported.  I just thought about it's possible application today and am astonished that the law professors mentioned below have not suggested its use.  Perhaps there IS some superseding law which would prevent its use but perhaps, like me, it is so little used that they just did not think of it either. 

I also understand that almost 300 noted legal scholars, including President Obama's former constitutional law professor Laurence Tribe, have signed a letter expressing their outrage at his continued imprisonment and the conditions.  See the news article written by Ed Pilkington in the Guardian.co.uk on Sunday April 10, 2011,  giving further references at:

http://www.guardian.co.uk/world/2011/apr/10/bradley-manning-legal-scholars-letter

 See the laws relative to the law of habeas and the military at: http://www.usconstitution. net/consttop_mlaw.html 
.  The actual discussion specific to habeas is in the middle of it. It
has referenced that military justice could possibly be appealed even out of the civilian courts to the Supreme Court in some cases. I think some good attorneys
with the capability and resources could and should pursue this course for him. The Writ of Habeas Corpus seems perfect for the use
of it.
At any rate if anyone has any knowledge why it couldn't or shouldn't be tried, please comment.