Updated

The U.S. Sentencing Commission on Thursday endorsed shorter federal prison sentences for most drug dealers -- but not before members of the agency scolded Attorney General Eric Holder for unilaterally pushing those changes weeks earlier.

"That unprecedented instruction disrespected our statutory role," said Judge William H. Pryor Jr., who sits on the commission.

The vote still was a win for Holder, who endorsed the proposal at a meeting of the commission last month. In a statement Thursday, he called the commission's action a "milestone in our effort to reshape the criminal justice system's approach to dealing with drug offenses."

But members of the commission used Thursday's meeting to publicly warn Holder against end-running the agency. The independence agency is tasked with establishing sentencing policies for the federal courts and advising Congress. Even these recommendations are supposed to go to Congress for approval, despite Holder's effort to push them now.

"The law provides the executive no authority to establish national sentencing policies based on speculation about how we and Congress might vote on a proposed amendment," Pryor said.

Members voiced concern that Holder had instructed federal prosecutors across the country not to object when defense attorneys tried to apply the proposal -- even though the proposal had not yet been approved.

"It would have been nice for us to have known ... that this action had been taken," Judge Ricardo Hinojosa said.

Despite the scolding, the decision advances Holder's efforts to ease long mandatory sentences and give greater discretion for judges in sentencing.

The commission said it estimates the changes approved Thursday would affect roughly 70 percent of federal drug trafficking defendants and would reduce by 11 months the average length of sentence for drug offenders.

The commission believes the change, which would reduce the sentencing guideline levels across drug types, would cut the federal prison population by more than 6,500 over five years.

The Associated Press contributed to this report.