Updated

Muslim convert Zachary Chesser of Virginia was very much on law enforcement's radar after posting threats against the creators of "South Park" for cartoons he felt insulted the prophet Muhammad.

Then he tried to join a terror group in Somalia, and went to the airport with his baby, hoping that would make him appear less suspicious.

It didn't work — stopped by the no-fly list, he was arrested and sentenced to 25 years in prison for attempting to support terrorist groups. He also pleaded guilty to threatening violence online.

Chesser, 25, now lives in the Supermax prison in Florence, Colorado. His wife, a Ugandan diplomat's daughter named Proscovia Nzabanita, had to leave the United States in early 2011 after pleading guilty to lying about his plans the year before.

The fate of their baby, Talhah, now 5 years old, remains at the center of a dispute being heard in federal appellate court on Thursday.

Chesser is suing the FBI and his own mother, alleging that agents interfered with his parental rights by conspiring with his mother and her partner to ensure that the boy could not travel to Jordan to live with his wife.

Instead, the boy is being raised by his mother, Barbara Chesser, a senior lawyer in the Office of the Attorney General in the District of Columbia, and her partner, who also is named as a defendant.

Chesser was behind bars and Nzabanita was facing deportation when his mother initiated custody proceedings, but both still enjoyed full parental rights, and they "opposed placing the young boy with his grandparents, who did not share Chesser and his wife's conservative Islamic beliefs," his court-appointed attorney, Wayne LaFond, says in their appeal.

But Chesser isn't seeking custody. Instead, he wants monetary damages.

Talhah was born in November 2009 to Chesser and his wife, a woman he met at a Washington, D.C., area mosque. They planned to travel together to Somalia where he would join al-Shabab, but Nzabanita's mother hid her passport.

Then, in the summer of 2010, they tried again. This time, Nzabanita dropped off Chesser and the baby to make the trip without her. Soon, they were both arrested. Chesser was facing a lengthy prison sentence, and Nzabanita struck a plea deal requiring her to leave the country, likely for good.

According to Chesser's complaint, agents monitoring his prison conversations in January 2011 tipped off Barbara Chesser that the young couple was making plans for a friend to take the boy to Jordan and join Nzabanita there.

Chesser's complaint states that agents went to the airport to stop that trip. Soon thereafter, Barbara Chesser won full custody of the boy after a judge declared Chesser and Nzabanita to be unfit parents.

LaFond argues that the FBI had no business disclosing the content of his conversations to intervene in a family custody dispute.

"Prisoners largely lose the right to keep secrets from the government," he wrote, but "they retain the right to keep those secrets from those outside the government."

Chesser was acting as his own lawyer when he first sued, in 2013. Judge Liam O'Grady dismissed that complaint, which remains under seal, as delusional and irrational. Chesser then amended his complaint, saying the essential facts remain accurate.

"It might not be particularly normal for the FBI to become so involved in a child custody proceeding ... but the scenarios described in the amended Complaint are far from fanciful," he wrote.

O'Grady again dismissed the lawsuit, saying Chesser had no expectation of privacy for conversations that occurred in a prison setting and therefore no reason to object when the FBI disclosed the conversation to his mother.

The 4th U.S. Circuit Court of Appeals in Richmond appointed LaFond to handle Chesser's appeal.

"Nothing alleged by Chesser is irrational or incredible. Chesser's complaint alleges that government agents misused confidential information they had gathered about him," LaFond wrote.

Lawyers for the FBI agents want a ruling that their actions are completely legal.

They wrote that no precedent exists "remotely suggesting that the disclosure of a parent's travel plans for a child can violate the parent's constitutional right to privacy," especially when the disclosure revolves around plans to relocate a child out of the country ahead of a custody hearing.

Barbara Chesser did not return calls seeking comment.

This damages dispute is just the latest unusual turn in this saga. Addressing Chesser at his sentencing in 2011, O'Grady said he "took just a shocking leap from a high-school athlete to a highly energized traitor."

Chesser's lawyers described a young man casting about for an identity, throwing himself headlong into whatever hobby consumed him. He joined a Korean breakdancing team, and became so fascinated with Japanese anime that he spent four years studying Japanese and traveled to Japan on a school trip.

Then, he converted to Islam after becoming infatuated during his senior year with the daughter of Somali immigrants. That ended when he demanded they marry. Chesser's divorced father said his son became so radical, he was "even wearing some type of loin cloth in place of underwear."

Chesser's name resurfaced in the news earlier this year when the FBI named a "close associate" of his in northern Virginia, Liban Mohamed, to its list of most-wanted terrorists.