The federal agency that sets criminal sentencing policies for judges voted on Friday to allow tens of thousands of inmates serving time for drug crimes to apply for reduced sentences, the largest such sentencing reduction in modern U.S. history.

The unanimous vote by the seven members of the U.S. Sentencing Commission will apply to most drug offenders in federal prisons, according to the commission.

Their decision came after the commission studied the results of a similar 2007 vote that affected only those serving time for crack cocaine offenses and found that inmates released early posed no greater risk of committing another crime than those who served their full terms.

“This amendment received unanimous support from the commissioners because it is a nuanced approach,” said Judge Patti Saris, the chair of the commission, in a statement.

Congress has until November 1 to disapprove of the commission’s decision. If lawmakers let the new rules stand, judges across the country can begin considering individual petitions from inmates for sentence reductions, but no prisoners can be released until Nov. 1, 2015, according to a special rule added by the commissioners.

Saris said the delay was intended to protect public safety by allowing time for judges to make an “appropriate consideration” of each petition.

The mass offer of sentence reductions comes amid a wave of bipartisan support for criminal justice reform that has gained momentum in the final years of President Barack Obama’s administration.

Obama and Attorney General Eric Holder have said they strongly support new policies that place less emphasis on prosecuting the kind of low-level, non-violent drug offenders who make up a large part of the federal prison population, which currently stands at around 216,000 people, exceeding capacity by 32 percent.

“This vote will change the lives of tens of thousands of families whose loved ones were given overly long drug sentences,” said Julie Stewart, the president of Families Against Mandatory Minimums, in a statement.

According to the commission, 46,290 inmates would be eligible for reduced sentences, with each likely to receive an average reduction of roughly two years.

Of the eligible inmates, roughly 28 percent are serving time for trafficking methamphetamine, and a similar number are serving time for powder cocaine offenses, according to statistics compiled by the commission. Smaller numbers of prisoners are serving sentences for trafficking crack cocaine, marijuana, heroin and oxycodone.

The commission estimates that around 4,600 inmates will receive sentence reductions that exceed the amount of time left in their prison terms, making them eligible for immediate release, though under the special rule they would not be let out until next November.

In April, the commission voted to amend its sentencing guidlines by lowering what are known as "offense levels," a 43-tier system designed by Congress and the commission that is used by judges to sentence all criminal defendants.

The April vote lowered each offense level for drug crimes by two, and Friday's vote made it retroactive. That effectively means, for example, that a person whose trafficking of 280 grams of crack cocaine would have once triggered a sentence range of 10 to 12-and-a-half years would now face a range of eight to 10 years.

A separate effort to extend clemency to thousands of other drug offenders is also underway. That effort, previewed in January and officially unveiled in April, would see the Justice Department's Office of the Pardon Attorney coordinate with a range of pro bono attorneys and federal public defenders known as the Clemency Project to screen clemency applications for approval by Obama.

But that effort remains in its early stages, and it has been the subject of ongoing concern by some involved that bureaucratic headaches and politics could hamstring the process.

The commission's decision is different, as it will impact a far larger number of inmates and is likely to proceed with less administrative delay.

In a statement released after the vote, Holder said he approved of the decision and would order the Bureau of Prisons to begin notifying inmates immediately of their eligibility to apply.

“This is a milestone in the effort to make more efficient use of our law enforcement resources and to ease the burden on our overcrowded prison system,” he said.

He also praised the yearlong delay before any inmates would be released as an adequate way to address concerns about public safety.

The Justice Department had previously objected to such a broad sentence reduction. At one of the Sentencing Commission's public hearings about the proposed change in June, federal prosecutor Sally Yates, representing the Justice Department, argued for excluding at least 20,000 inmates from consideration.

The department’s plan, as articulated by Yates, would have made sentence reductions available only to prisoners with extremely limited criminal histories whose crimes had involved no weapons or violence and who had not obstructed justice.

Advocates for sentencing reform argued that such a categorical denial to so many inmates would exclude many worthy candidates with specific and sympathetic cases whose petitions would never have a chance to reach a judge’s consideration.

In April, the commission voted unanimously to reduce sentencing guidelines for most drug offenders going forward. In the months that followed, the commission received more than 60,000 letters regarding whether those reduced guidelines should be made retroactive. The letters “overwhelmingly favored” reducing old sentences, according to the commission.