In April of this year, Saadiq Long, a 43-year-old African-American Muslim who now lives in Qatar, purchased a ticket on KLM Airlines to travel to Oklahoma, the state where he grew up. Long, a 10-year veteran of the US Air Force, had learned that the congestive heart failure from which his mother suffers had worsened, and she was eager to see her son. He had last seen his mother and siblings more than a decade ago, when he returned to the US in 2001, and spent months saving the money to purchase the ticket and arranging to be away from work.

The day before he was to travel, a KLM representative called Long and informed him that the airlines could not allow him to board the flight. That, she explained, was because the US Department of Homeland Security (DHS) had placed Long on its "no-fly list", which bars him from flying into his own country.

Long has now spent the last six months trying to find out why he was placed on this list and what he can do to get off of it. He has had no success, unable to obtain even the most basic information about what caused his own government to deprive him of this right to travel.

He has no idea when he was put on this list, who decided to put him on it, or the reasons for his inclusion. He has never been convicted of any crime, never been indicted or charged with a crime, and until he was less than 24 hours away from boarding that KLM flight back to his childhood home, had received no notice that his own government prohibited him from flying.

As his mother's health declines, he remains effectively barred from returning to see her. "My mother is much too sick to come visit me, as she has difficulty now even walking very short distances," Long told me in an interview Sunday in Doha, the sleek, booming capital city of America's close Gulf ally, where the former Senior Airman and Staff Sergeant has lived for several years.

"I don't understand how the government can take away my right to travel without even telling me," he said. What is most mystifying to him is that he has spent the last decade living and working, usually teaching English, in three countries that have been very close and compliant US allies: Egypt, United Arab Emirates, and now Qatar. "If the US government wanted me to question or arrest or prosecute me, they could have had me in a minute. But there are no charges, no accusations, nothing."

As compelling as Long's story is, it is extremely common. Last year in Washington, I met a 19-year-old Somali-American Muslim, born and raised in the US, who saved money from a summer job to purchase a ticket to travel for the first time to Somalia to visit family members he had never met. When he went to the ticket counter to check-in, he was informed that he was barred from flying and suffered the humiliation of having to return home with his luggage and then trying to explain to his employer, family and friends why he did not travel.

Like Long, that American teenager was never convicted or even charged with any crime, and was mystified and angry that his own government secretly placed him on this list, though he remains too afraid to speak out without anonymity. "I'm scared that if I do, it'll only get worse," he told me.

Like so many post-9/11 civil liberties abridgments aimed primarily at Muslims, this no-fly-list abuse has worsened considerably during the Obama presidency. In February, Associated Press learned that "the Obama administration has more than doubled, to about 21,000 names, its secret list of suspected terrorists who are banned from flying to or within the United States, including about 500 Americans."

Worse, the Obama administration "lowered the bar for being added to the list". As a result, reported AP, "now a person doesn't have to be considered only a threat to aviation to be placed on the no-fly list" but can be included if they "are considered a broader threat to domestic or international security", a vague status determined in the sole and unchecked discretion of unseen DHS bureaucrats.

But the worst cases are those like Long's: when the person is suddenly barred from flying when they are outside of the US, often on the other side of the world. As a practical matter, that government act effectively exiles them from their own country. "Obviously, I can't get to Oklahoma from Qatar if I can't fly," said Long. "Trying to take a boat would take weeks away from work just for the travel alone, and it's not affordable. If I can't fly, then I can't go back home."

Gadeir Abbas, a lawyer with the Council on American-Islamic Relations (CAIR) now working on Long's case, told me:

"What is happening to Saadiq happens to American Muslims with alarming regularity. Every few weeks I hear of another Muslim citizen who cannot return to the country of which he is a citizen. "It is as if the US has created a system of secret law whereby certain behaviors - being Muslim seems to be one of them - trigger one's placement on government watch lists that separate people from their families, end careers, and poison personal relationships. All of this done without any due process."

The ACLU has spent years challenging the constitutionality of the no-fly list in court. Representing 15 US citizens and permanent residents who have been placed on the list, including four military veterans, the civil liberties group scored a possibly significant victory this June when the 9th Circuit of Appeals reinstated their lawsuit, which a lower court judge had dismissed, and allowed the case to proceed. ACLU lawyer Nusrat Choudhury, who argued the case, told me:

"The No Fly List bars thousands of people from commercial air travel without any opportunity to learn about or refute the basis for their inclusion on the list. The result is a vast and growing list of individuals who, on the basis of error or innuendo, have been deemed too dangerous to fly but who are too harmless to arrest. Some have been stranded abroad when they suddenly found themselves unable to board planes. "None of these Americans have ever been told why they are on the No Fly List or given a reasonable opportunity to get off it. But, the Constitution requires the government to provide our clients a fair chance to clear their names."

Long's case is both typical yet particularly compelling. Strictly on humanitarian grounds, it is outright cruel to deny a person who has been convicted of no crime the ability to see his ailing mother.

Beyond the constitutional and humanitarian questions, Long was confounded by what seems to be the utterly irrational reasoning on which the no-fly list is based. As it bars him only from flying, he remains technically free to board a cruise ship to the US, one that would be filled with American civilians. Every US citizen has the constitutional right to enter the country, so he is technically free to visit the US or return there to live if he is able to get back, to visit crowded streets and shopping malls, to board trains, in essence to do anything but fly.

"It makes no sense, so it's obvious this is meant as some kind of punishment, but for what?", he asked. "If they are so afraid of me, they can just put a law enforcement agent on the plane to escort me back home."

After learning he had been barred from flying, Long sought assistance from the US Embassy in Doha. "After many follow-up calls to the embassy," he recounted, "they finally gave me 'assistance' in the form of the website to DHS and instructions to file a complaint." On 15 May, he filed a formal complaint with DHS and received a so-called "redress control number" with a promise to review his case within 7-10 business days. Almost six months later, he is still in Doha waiting for an answer, still harboring hope that he will receive clearance to return home to visit his sick mother.

Abbas, the CAIR lawyer, told me: "It makes my stomach churn what the US does to American Muslims while they travel." Unfortunately, he said, the political reality of this issue tracks the familiar pattern of Muslims being denied the most basic rights: "there is zero political will to alter the use of endless secret watchlists that terrorize the Muslim community and make none of us any safer."

Abbas worked last year on the truly wrenching case of Gulet Mohamed, the then-18-year-old Somali-American who, while visiting Kuwait, was detained at the behest of the Obama administration, and beaten and tortured by Kuwaiti authorities while he was interrogated for two weeks. Once the Kuwaitis were done with him and wanted to release him, Mohamed - who, to date, has never been charged with any crime - faced a horrible dilemma: at some point when he was traveling, the US government placed him on a no-fly list, meaning that he could no longer stay in Kuwait, but also could not return to the US, stuck in lawless limbo.

When he was in Kuwaiti detention, Gulet was able to use a cell phone illicitly obtained by a fellow detainee, and his family arranged for him to call me and the New York Times' Mark Mazzetti to recount his story. I spent an hour on the phone with him, and still vividly recall the terror and visceral fear of the American teenager as he tried to understand why his own government first arranged for his detention and beating, and then barred him from returning to the country where he was born and had lived his whole life, even when the Kuwaitis were eager to release him. That is the tyranny of the no-fly list.

"Our litigation in Gulet Mohamed's case seeks to establish what I think is the very modest proposition that the US cannot actively obstruct a citizen's movement into the US from abroad," said Abbas. As modest - and self-evident - a proposition as that is, it is one the US courts have not recognized in the context of no-fly lists.

Saddiq Long has now purchased another ticket to travel to the US on 8 November, less than a week from now, in the hope that the US government will allow him to fly. "If he isn't allowed to fly home on the 8th," said Abbas, "we will plan on mobilizing people to contact the Special Agent in Charge of the FBI field office in Oklahoma City. The FBI controls these lists and his intervention could end Saadiq's predicament."

For now, Long can do nothing other than wait and hope that his own country, which he served for a decade in the armed forces, will deign to allow him to return. Secret deprivation of core rights, no recourse, no due process, no right even to learn what has been done to you despite zero evidence of wrongdoing: that is the life of many American Muslims in the post-9/11 world. Most significantly, it gets progressively worse, not better, as the temporal distance from 9/11 grows.