Former Mashantucket Pequot Chairman Michael Thomas is appealing his conviction on federal theft charges, claiming a judge erred when she prevented him from arguing that he intended to repay the more than $100,000 he embezzled from the tribe that owns Foxwoods Resort Casino.

In a filing Wednesday in the 2nd U.S. Circuit Court of Appeals, Thomas, currently serving an 18-month prison term, asks that he be granted a new trial.

Thomas' court brief, written by West Haven attorney Steven Rasile, claims Thomas should have been allowed to introduce evidence at his trial that he intended to reimburse the tribe for personal expenses he charged to a tribe-issued American Express card that was to be used only for business purposes.

He also should have been permitted to show that other members of the tribal council used their tribe-issued credit cards for personal expenses, Rasile writes.

Following pretrial hearings, U.S. District Judge Janet Bond Arterton, who presided at the trial, granted prosecution motions barring the defenses.

"The Appellant's intent to repay, when coupled with the Tribe's practice of permitting the Appellant to place personal expenses on the Tribe's charge card and reimburse them later could have demonstrated that the defendant lacked the requisite intent to commit the crimes with which he was charged," the brief says.

Rasile argues that Arterton "abused her discretion," violating Thomas' constitutional right to defend himself.

Asked for comment on the appeal, a spokesman for the U.S. Attorney's Office in Connecticut said, "We'll respond in court."

Thomas was indicted in January 2013 on one count of theft from an Indian tribal organization and two counts of theft from an Indian tribal government receiving federal funds. In July, a jury in New Haven found him guilty on all counts.

Most of Thomas' improper credit-card charges — $89,000 worth, according to the appeal brief — were for his dying mother's limousine rides to and from a New London dialysis center.

During the period outlined in the indictment, October 2007 to September 2009, Thomas was chairman of the Mashantucket tribe.

Thomas began serving his sentence at FMC Devins, a federal facility in Ayer, Mass., in January. Following his prison term, he faces 36 months of supervised release and must make restitution to the tribe.

Last month, the tribe's elder members moved to "banish" Thomas from the Mashantucket reservation "and all tribal lands."

Thomas' younger brother, Steven, who was indicted along with him and who pleaded guilty to a single count of theft, was sentenced in February to two years of supervised release, the first three months of which were to be served in home confinement.

Steven Thomas, who admitted to falsifying time cards while working for tribal government, resigned as tribal treasurer before entering his plea. While awaiting sentencing, he was hired to work in Foxwoods' human resources department. He, too, was banished, though not from his home on the reservation, from Foxwoods or from other locations related to his job.

b.hallenbeck@theday.com