— The North Carolina Supreme Court ruled Friday that a convicted killer serving a life sentence under a 40-year-old law cannot use credits for good behavior to reduce the length of his sentence.

The court reversed a 2013 ruling from the state Court of Appeals, which had upheld a Superior Court judge's ruling that Bobby Bowden, 65, be released from prison under a 1974 North Carolina law that defined a life sentence as 80 years in prison.

Bowden is serving two concurrent life sentences for the Aug. 7, 1975, shootings at a Cumberland County convenience store. He was convicted of two counts of first-degree murder and one count of armed robbery on Dec. 15, 1975.

Before the state's Fair Sentencing Act, which took effect in 1994, guidelines allowed prisoners to earn credit toward their release for good behavior.

Bowden's lawyers contend that he has earned enough credits to be eligible for release without conditions. Numerous other inmates whose death sentences were commuted to life in prison under the old law have made similar arguments in recent years.

The Supreme Court ruled in a 4-2 decision, however, that Bowden isn't eligible to have his sentence reduced. The credits he receives in prison can only earn him extra benefits behind bars or move up his parole eligibility, Associate Justice Paul Newby wrote in the court's opinion.

"The (state prison system) has never applied these credits towards the calculation of an unconditional release date for a (similarly situated) inmate. Therefore, we hold that defendant ... remains lawfully incarcerated and is not entitled to release," Newby wrote.

Four years ago, the court reached a similar conclusion in the cases of two other convicted killers, ruling that state prisons officials and the parole board should determine when inmates get out.

Associate Justice Robin Hudson strongly disagreed with the majority, ruling that lower courts made a factual finding that prison officials had applied Bowden's credits to his release date.

"The State is under no obligation to create or to award credits that reduce a prisoner’s sentence for a crime for which he was lawfully convicted. But once it does so, it cannot then arbitrarily and with no process take those credits back," Hudson wrote in a dissent that Associate Justice Cheri Beasley joined.