(CNN)After two days of walking in the Syrian desert, one fitful night sleeping in a mud hut and a failed attempt to bribe a local into vouching for him to get safe passage out of ISIS territory, it looked like the man was en route to freedom on the back of a water truck.
The US wants to leave this American in Syria with $4,210 and no passport
But when the truck reached a checkpoint near Abu Khashab guarded by Syrian Democratic Forces, a soldier spotted the man and asked him to climb down, according to court documents.
The Kurds had set up the checkpoint to stop Islamic State fighters from fleeing the area by hiding with groups of refugees. The soldier was suspicious of the man, who had a long beard, stylish clothing and a duffel bag containing a Quran, a GPS device, flash drives, $4,210 in cash and, oddly, a snorkel mask and a scuba certification card.
Among the files on the flash drives were bomb-making manuals and an array of Arabic spreadsheets, including one named "Islamic State Spoils and Booty Bureau."
It was on or about September 11, 2017, when the Kurdish soldiers apprehended the man, according to court filings. He told his captors he was a US citizen and asked them to take him to the Americans. The Americans took him to a safe house for two days of interrogations by government agents.
He said he had journeyed to Syria as a freelance journalist and was kidnapped by ISIS within days of crossing the border from Turkey. He denied that he was a fighter and said he had made multiple escape attempts over 30 months in the terror group's self-declared caliphate.
After telling the agents his story, the man was blindfolded and transported via helicopter to a military prison at a classified location in Iraq, where he has been locked up for more than nine months as an alleged enemy combatant.
In a federal courthouse 6,000 miles from Iraq, there's an ongoing dispute over the fate of the mysterious detainee caught in the desert with scuba gear and ISIS spreadsheets. In court documents, the prisoner is called John Doe because of the secrecy surrounding the case. Doe has yet to be charged with a crime.
The American Civil Liberties Union argues that the Department of Defense should either bring Doe to the US for prosecution or release him. It's a case straight out of TV's "Black Mirror," with ACLU lawyers encouraging the government to arrest their client.
Keeping an American citizen in military custody abroad is a violation of due process rights, according to the ACLU. The organization filed its petition for a writ of habeas corpus at the US District Court for the District of Columbia last October.
The government says the Authorization for Use of Military Force passed by Congress in 2001 gives the executive branch wide latitude to detain individuals, including American citizens, captured on the battlefield to prevent acts of terrorism.
The problem, according to the ACLU, is that there's no end point to the war on terror, so the military can imprison someone indefinitely. The government's burden of proof goes out the window if a detainee isn't permitted to challenge the factual basis for his designation as an enemy combatant.
Airstrikes on the Islamic State began in 2014 and at the time, the Obama administration reasoned that the military could carry out attacks without congressional approval because the 2001 Authorization for Use of Military Force covered groups associated with al Qaeda. ISIS evolved out of an al Qaeda splinter group.
In a 147-page court filing, the Defense Department presented its evidence that Doe had provided material support to the Islamic State. The overview is heavy on internet search histories and social media postings. Between January 2014 and March 2015, according to the Defense Department, Doe looked up ISIS videos on YouTube 859 times. He sent 22 tweets to an Islamic State propaganda account, posting pictures of the group's flag and denouncing "infidels." In one tweet, he declared, "Let's unite that the word of God may be realized in us and that we may cut off the hand and cut out the tongue of the troublemakers."
Although an internal ISIS intake form recovered during military operations lists Doe as a fighter, he said he was never much of a mujahedeen due to back problems. He told government agents he spent his first seven months in Syria jailed by ISIS. At some point, he was released on the condition that he work for the terror group. Doe then registered as an Islamic State recruit, swore an oath and went to a Sharia training facility.
While living in the caliphate, Doe served in various administrative roles. He described a life of banal chores rather than battlefield savagery. Doe guarded an oil field, gassed up vehicles and monitored prayer services. At one point, an ISIS commander asked him to help build a device that could take down airplanes via microwaves. Doe said he refused to work on the project. Instead, he paid the Islamic State $750 to rent a 200-acre farm in Hamah, planting almond and olive trees, tending to a flock of 80 sheep. He envisioned himself starting a new life as a shepherd across the border in Turkey. The looming danger of airstrikes motivated him to sell his sheep, flee the farm and try to escape via water truck, Doe told the interrogators.
While other American travelers suspected of ISIS support have been extradited to the US and charged in criminal court, there are no signs the government intends to prosecute Doe. In April, the Defense Department said it was prepping to transfer him to authorities in an unnamed third country. The third country is likely Saudi Arabia, where Doe holds dual citizenship, according to court documents. The transfer was stopped by a district judge. An appeals court panel upheld her ruling.