He is an Australian prisoner and was punished by US military tribunal since he had provided material support to terrorists
"The 31-year-old former kangaroo skinner was accused of fighting for al Qaeda in Afghanistan during the U.S.-led invasion in 2001 and has been held at Guantanamo for more than five years. He announced his decision at a hearing in the U.S. war crimes tribunal at the base. " The answer for this by Hicks was
"YES".
If he is found that he had done the mistake. He would be surely punished for life time imprisonment. The judge ordered the prosecutors and defense lawyers to draw up a plea agreement by 4 p.m. ET (2000 GMT) on Tuesday,which would finally decide what type of sentence he would serve.
What ever the sentence may be he would be served that in Australia.