WASHINGTON — Tens of thousands of federal inmates serving time for drug crimes may be eligible for early release under a cost-cutting proposal adopted Friday that would dramatically reduce the nation’s prison population over time.
The US Sentencing Commission, which earlier this year voted to substantially lower recommended sentences for drug-dealing felons, voted unanimously to retroactively apply that change to prisoners now behind bars.
More than 46,000 inmates, including many who have already served a decade or longer in prison, would be eligible to seek early release under the commission’s decision. The commission, an independent panel that sets sentencing policy, has said sentences would be cut by an average of 25 months. The releases would start in November 2015 and be phased in over a period of years.
‘‘The magnitude of the change, both collectively and for individual offenders, is significant,’’ commission chairwoman Patti Saris, a federal judge in Massachusetts, said before the vote.
Advocates of the early-release plan say it would cut prison costs — nearly one-half of the federal prison population is locked up for drug crimes — and scale back some of the harsh sentences imposed during the country’s war on drugs. Prisoner advocacy groups immediately trumpeted the change, calling it a matter of fundamental fairness.
‘‘This vote will change the lives of tens of thousands of families whose loved ones were given overly long drug sentences,’’ Julie Stewart, president of Families Against Mandatory Minimums, said in a statement.
The change is part of a broader rethinking of criminal justice policy that the Justice Department, under Attorney General Eric Holder, has embraced. With an eye toward addressing sentencing disparities rooted in the 1980’s-era fight against crack cocaine, the Justice Department has issued new clemency criteria designed to encourage thousands of additional inmates to seek clemency. Last year, Holder directed federal prosecutors to avoid seeking mandatory minimum sentences for nonviolent drug offenders.
‘‘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,’’ Holder said in a statement.
Though sentencing guidelines are advisory rather than mandatory, judges still rely heavily on them in deciding on prison sentences. The guidelines recommend sentences that factor in the types and quantities of the drugs. The commission in April voted to lower recommended sentences across all drug types, meaning, for instance, that a cocaine package of a given size would now be linked to a shorter range of punishment than before.
Congress has until November to voice opposition to the commission’s plan, though advocates consider that unlikely.