(CNN) A federal judge has blocked the execution of an inmate that Arkansas prison authorities planned to put to death alongside seven other convicts later this month.

Gov. Asa Hutchinson announced a controversial plan in March to execute eight inmates over a 10-day period starting on April 17. Arkansas must carry out the executions before its supply of a lethal injection drug expires at the end of April.

US District Judge DP Marshall Jr.'s ruling on Thursday came a day after the state's parole board voted 6-1 to recommend that Jason McGehee's death sentence be commuted to life without parole.

McGehee and two co-defendants, Christopher Epps and Benjamin McFarland, were convicted of a 1996 murder in Boone County, Arkansas.

"Mr. McGehee was only twenty years old at the time of his offense, and his near-perfect record in prison has impressed many people," John Williams, McGehee's lawyer, said in a statement Wednesday.

"The parole board determined Mr. McGehee warrants clemency instead of death because of his exemplary behavior, his youth at the time of the crime, and also because his sentence is not proportional," he said.

McGehee's two co-defendants took plea deals and received lesser sentences. Epps was remanded to life in prison; McFarland was ordered to serve 40 years.

In his ruling on Thursday, Marshall said the state could not execute McGehee on his scheduled date of April 27 because Arkansas law requires that the parole board be given a 30-day period to notify the governor of a clemency recommendation. Hutchinson's schedule would have prevented the parole board from complying with state law.

Marshall's decision means McGehee cannot be executed until after the state's supply of midazolam, the first drug administered in lethal injection protocol, expires. It is unclear if or when McGehee's execution will be rescheduled. Hutchinson must ultimately decide on whether to grant clemency.

The ruling was hailed a victory by death penalty critics.

"All of the scheduled executions must be halted for good," said James Clark, a campaigner with Amnesty International USA, said in a statement. "While the death penalty is unacceptable in any case, the judicial process should not be cut short for something as trivial as an expiration date when the stakes are so high."

Hutchinson said last week that it is his duty to carry out the executions before the drug expires.

"In order to fulfill my duty as Governor, which is to carry out these lawful sentences imposed by juries and upheld by the Arkansas Supreme Court, it is necessary to schedule the executions prior to the expiration of that drug," Hutchinson said in a statement sent to CNN.

Midazolam, which is used to render inmates insensate, has been blamed as the cause of multiple botched executions across the country in recent years. Most recently, in December, Alabama inmate Ronald B. Smith reportedly struggled and coughed as his execution was being carried out. Reports of botched executions have also emerged from Texas, Georgia, Florida, Oklahoma, Ohio, Illinois and Arizona.

Attorneys for the inmates have launched several legal complaints at both the federal and state level to try and derail the execution schedule. They accuse Gov. Hutchinson and the Arkansas Department of Corrections of violating the inmates' rights to due process and Eighth Amendment protections from cruel and unusual punishment.

Only Texas has ever conducted eight executions in a single calendar month since the resumption of the death penalty in 1977, according to Robert Dunham, executive director of the Death Penalty Information Center in Washington D.C. No state has ever executed eight inmates in as few as 10 days.