The Justice Department is preparing to release roughly 6,000 inmates from federal prisons starting at the end of this month as part of an effort to ease overcrowding and roll back the harsh penalties given to nonviolent drug dealers in the 1980s and ’90s, according to federal law enforcement officials.
About a third of the inmates are undocumented immigrants who will be deported. Because many of them were convicted of significant legal offenses, President Obama is unlikely to be criticized as sharply for their release by those who have objected to past deportations by the administration.
The release will be one of the largest discharges of inmates from federal prisons in American history. It coincides with an intensifying bipartisan effort to ease the mass incarcerations that followed decades of tough sentencing for drug offenses — like dealing crack cocaine — which have taken a particularly harsh toll on minority communities.
“Today’s announcement is nothing short of thrilling because it carries justice,” said Jesselyn McCurdy, a senior legislative counsel at the American Civil Liberties Union. “Far too many people have lost years of their lives to draconian sentencing laws born of the failed drug war. People of color have had to bear the brunt of these misguided and cruel policies. We are overjoyed that some of the people so wronged will get their freedom back.”
While news of the early releases was widely praised, it raised some concerns among law enforcement officials across the country who are grappling with an increase in homicides. Their fear is that many of the freed convicts will be unable to get jobs and will return to crime.
Ronald E. Teachman, who was the police chief in South Bend, Ind., until last Wednesday, said inmates were not always convicted of all the crimes they had committed.
He also said that prisoners who were released after receiving job skills and other assimilation training often succeeded. But that rarely occurs, he said — even in the federal system.
“People come out of prison hardened and angry and more likely to offend,” said Mr. Teachman, now an executive with ShotSpotter, a company that promotes a system for detecting gunfire.
In April 2014, the United States Sentencing Commission reduced the penalties for many nonviolent drug crimes. That summer it said those guidelines could be applied retroactively to many prisoners serving long drug sentences. Eric H. Holder Jr., the attorney general at the time, had lobbied the sentencing commission to make the changes.
Under the new guidelines, prisoners can ask federal judges to reassess their sentences. Along with examining the inmates’ behavior in prison, the judges look at whether they are likely to act out violently if they are released.
As part of an effort to give the federal Bureau of Prisons time to prepare for an influx of convicts entering probation and re-entry programs, the releases were delayed. They will now take place from Oct. 30 to Nov. 2.
“The Sentencing Commission’s actions — which create modest reductions for drug offenders — is a step toward these necessary reforms,” said Sally Q. Yates, the deputy attorney general. “Even with the Sentencing Commission’s reductions, drug offenders will have served substantial prison sentences.”
The United States has a quarter of the world’s prison population, and Republican and Democratic lawmakers agree that prison spending, which accounts for a third of the Justice Department’s budget, needs to be reduced.
Last week, a bipartisan group of senators proposed a sweeping overhaul aimed at reducing mandatory minimums and winning early release for those serving sentences disproportionate to their crimes.
The changes would be retroactive if the legislation is enacted, and lawmakers estimated that up to 6,500 other prisoners — many of them charged with offenses related to crack cocaine — could qualify for resentencing under the changes. Given the bipartisan support, the legislation has a stronger chance of being passed than many other bills Congress is considering.
Immigrant advocates have accused the administration of breaking up families by deporting immigrants who did little wrong other than coming to the country illegally. This criticism was fueled by a record number of deportations in Mr. Obama’s first term — although that pace has slowed considerably in the last year.
This summer, Republican candidates for president, particularly Donald J. Trump, seized on the killing of a woman on a San Francisco pier by a man who had been deported to Mexico several times and was recently freed from a federal prison.
Josh Earnest, the White House press secretary, on Tuesday declined to comment on the release of the prisoners, but expressed optimism that both parties would continue to support criminal justice changes.
“We’re pleased to see that many Republicans consider this to be a priority, too,” Mr. Earnest said. “At this point, I don’t think there’s a significant level of concern that any rhetoric on the campaign trail could sabotage the important bipartisan work that’s currently ongoing on Capitol Hill. And I hope I’m right about that.”
Anthony Papa, a spokesman at the Drug Policy Alliance, which supports the relaxation of certain drug sentencing laws, said, “It warms my heart to hear that 6,000 people will be coming home.”
“The drug war has devastated families and communities, and it is time for the healing to begin,” said Mr. Papa, who himself spent 12 years behind bars on a mandatory minimum drug sentence.