CHICAGO, Jan. 23 - The Illinois Supreme Court ruled on Friday that former Gov. George Ryan was within his authority in commuting the sentences of all prisoners on the state's death row.

The governor may grant reprieves, pardons and commutations on his own terms, and the decisions are "unreviewable," the court said.

Two days before he left office, on Jan. 11, 2003, Mr. Ryan, a Republican, criticized the capital punishment system as fundamentally flawed and unfair. He commuted the sentences of 167 people on death row and pardoned 4 others.

In their ruling on Friday, the justices said that Mr. Ryan's use of blanket clemency was unconventional and that they hoped that future governors would instead use it in individual cases. But, the court added, the state's Constitution supports Mr. Ryan's decision.

"The governor's constitutional clemency powers allow him to completely or partially absolve a defendant of the consequences of his crime, and to suspend or commute any
sentence imposed by the judiciary," Justice Robert R. Thomas wrote in the opinion.

Attorney General Lisa Madigan challenged Mr. Ryan, saying he did not have the authority to grant clemency to 32 prisoners, largely because they had failed to file clemency petitions and were therefore not subject to his decision.

The court said that Mr. Ryan considered the death penalty system broken and that "the failure of certain inmates to consent to their petitions was irrelevant to the governor."

Ms. Madigan said the governor granted clemency to inmates technically not on death row. Those inmates had been sentenced to death, but their sentences were reversed on appeal. The court disagreed, saying the prior sentences, though unenforceable, remained relevant.

In a statement, Ms. Madigan said: "Public faith in our state's criminal justice system has been shaken over recent years. It is my hope that today's Supreme Court ruling, combined with much-needed and groundbreaking death-penalty reforms, will help restore confidence in the integrity and effectiveness of that system."

Mr. Ryan, 69, was nominated last year for the Nobel Peace Prize for his work on the death penalty. He was indicted last month on charges of racketeering conspiracy, mail and tax fraud and lying to law enforcement officials. He has denied the charges.

The state's attorney in Lake County, Michael J. Waller, said he was not surprised by the Supreme Court decision. Mr. Waller acknowledged that Mr. Ryan had acted within the law but said clemency should be granted only case by case. The decision, the prosecutor added, may have spared the lives of deserving inmates, but it also removed some of the most violent offenders from death row.

"What Governor Ryan did," Mr. Waller said, "was grant relief in cases where it may have been appropriate. But in the overwhelming majority of these cases, relief was unjustified."

Rob Warden, executive director of the Center on Wrongful Convictions at Northwestern University, an organization that helped coordinate the clemency hearings and petitions, said he was confident that Mr. Ryan was acting within the law.

"We had been confident from the beginning that this would be the outcome," Mr. Warden said. "The Illinois Constitution seemed to be absolutely clear and unequivocal that the governor has the right to grant reprieve to anybody who stood convicted in the state of Illinois."