A Detroit man sentenced to life in prison as a teenager on a drug offense decades ago is not entitled to a new sentencing hearing, the Michigan appeals court ruled on Tuesday.

Richard Wershe, 46, known as "White Boy Rick," was convicted of possession with intent to deliver more than 650 grams (23 ounces) of cocaine and sentenced to life in prison without parole on the offense committed when he was 17 years old, according to court documents.

In September, Wayne County Circuit Judge Dana Hathaway granted Wershe a new hearing, finding that his original sentence was extraordinarily harsh for a nonviolent juvenile offender, according to court documents.

The Michigan Court of Appeals ruled, however, that Hathaway did not have the authority to overturn a sentence that was determined to be constitutional.

An attempt to resentence Wershe "may infringe upon the governor's commutation powers and intrude upon the parole board's jurisdiction," the judge's ruled.

Wershe's attorney Peter Van Hoek told the Detroit Free Press he was disappointed with the ruling and planned to take the case to the Michigan Supreme Court.

Unless overturned, Wershe's original sentence stands.

Wershe was convicted in 1988 at a time when the United States had enacted mandatory minimum sentences to fight rising crime and drug violence and has spent more than 27 years in prison.

According to a book about the case, Wershe drove around Detroit dealing drugs out of a Jeep with the words "The Snowman" on the back and claimed he had worked as an FBI informant since he was 14 years old.

(Reporting by Brendan O'Brien in Milwaukee; Editing by David Bailey and Eric Beech)