[cnn-photo-caption image= http://i2.cdn.turner.com/cnn/2009/CRIME/02/27/enemy.combatant.almarri/art.marri.gi.jpg caption="Ali Saleh Kahlah al-Marri was a student at Bradley University in Illinois when he was arrested in 2001."]
WASHINGTON (CNN) - A Qatari man held for years in military custody in the United States was charged Friday in federal court with conspiracy "to provide material support and resources" to al Qaeda, prosecutors announced.
The Supreme Court was to hear arguments in April on a challenge by the suspect, Ali Saleh Kahlah al-Marri, to the principle that the president has the authority to detain suspected terrorists indefinitely and without charges.
The indictment means the case will be transferred to civilian courts for prosecution.
The Supreme Court is likely to approve an expected request from federal prosecutors to dismiss the pending appeal before the justices.
The decision by the Obama administration to criminally charge al-Marri after he spent more than seven years in custody - more than five years in virtual isolation in a Navy brig in North Charleston, South Carolina - is the latest twist in the ongoing legal saga of the only remaining "enemy combatant" held in the United States.
He has been accused of - but until this indictment had never been charged with - being an al Qaeda "sleeper agent."