I honestly do not understand why any american citizen captured in battle against the US should be allowed to go free. I also don't understand why Irregulars caught in military operations need to be given trial or let free either, the British kept captured Boers in prison camps permanently (unless they signed an agreement to not take up arms again), why shouldn't the US?

However, I think a US citizen captured there should be tried in court. Taking up arms against the US is treason, and they should be executed for commiting it. If the government can't demonstrate that a person was actually fighting for the enemy, then why hold them at all? On the other hand, why would they even bother capturing him if he was doing nothing, it seems like they might not be able to prove to judicial standards that he is guilty, but that they have proved to themselves that he is. Regardless he seems inclined to return to Saudi anyway.