A prison law clerk who convinced the U.S. Supreme Court to hear a fellow inmate's case is being investigated by South Carolina authorities for practicing law without a license, the prisoner's attorney said Tuesday.

Lawyer Rauch Wise confirmed the state attorney general's office informed him last week they were investigating Michael Ray, a federal inmate in South Carolina. The Associated Press received a letter from Ray last week in which he claimed state authorities were investigating him.

Ray helped fellow inmate Keith Lavon Burgess appeal his conviction for possession of crack cocaine with the intent to distribute. In the appeal, which the U.S. Supreme Court is scheduled to hear on March 24, Burgess is arguing that a prior drug conviction prosecutors used to get him the 20-year minimum prison sentence shouldn't have applied because it was a misdemeanor instead of a felony.

Conflicting court rulings have required 10-year sentences for people already convicted of misdemeanors, so a successful appeal could trim Burgess' sentence in half.