The commission, which sets guidelines for federal prison sentences, decided to make retroactive its recent easing of recommended sentences for crack offenses.
Roughly 3,800 inmates could be eligible for release from prison within a year after the March 3 effective date of Tuesday's decision. Federal judges will have the final say whether to reduce sentences.
The commissioners said the delay would give judges and prison officials time to deal with public safety and other issues.
U.S. District Judge William Sessions of Vermont, a commission member, said the vote on retroactivity will have the "most dramatic impact on African-American families." A failure to act "may be taken by some as particularly unjust," Sessions said before the vote.
The seven-member commission took note of objections raised by the Bush administration, but said there is no basis to treat convicts sentenced before the guidelines were changed differently from those sentenced after the change.
Inmate family representatives and other advocates of retroactive easing said a Supreme Court decision Monday could only improve chances the commission would dismantle yet another portion of the long-criticized disparity in sentences for crack and powder cocaine offenses. Crack is predominantly used by blacks; powder cocaine, predominantly by whites.
In two decisions Monday, the Supreme Court upheld judges who rejected federal sentencing guidelines as too harsh and imposed more lenient prison terms, including one for crack offenses.
In the crack case, Justice Ruth Bader Ginsburg's majority opinion said Derrick Kimbrough's 15-year sentence was acceptable, although guidelines called for 19 to 22 years. "In making that determination, the judge may consider the disparity between the guidelines' treatment of crack and powder cocaine offenses," Ginsburg said.
Kimbrough is black.
So are 86 percent of the 19,500 inmates who might see their prison terms for crack offenses reduced if the commission approves retroactive easing. By contrast, just over a quarter of those convicted of powder cocaine crimes last year were black.
The sentencing commission recently changed the guidelines to reduce the disparity in prison time for the two crimes. New guidelines took effect Nov. 1.
Under the commission's plan, retroactive sentence reductions would not be automatic. A judge would have to review each inmate to decide whether a reduction was merited.
"The Kimbrough decision is a tremendous victory for all who believe that the crack and powder cocaine disparity is unjust," said Mary Price, vice president of Families Against Mandatory Minimums.
Kimbrough's case, though, did not present the ultimate fairness question. Congress wrote the harsher treatment for crack into a law that sets a mandatory minimum of five years in prison for trafficking in 5 grams of crack cocaine or 100 times as much powder cocaine.
Seventy percent of crack defendants get the mandatory minimum.
Kimbrough is among the remaining 30 percent who, under the guidelines, are supposed to receive even more prison time for trafficking in more than 5 grams of crack.
Neither the court's decision nor the commission's guidelines affect the minimum sentences, which only Congress can alter.
"The ruling isn't going to immediately guarantee crack cocaine convicts a slap on the wrist," says CBS News senior legal analyst Andrew Cohen. "In fact, judges still can throw the book at them with very significant penalties that go far beyond what someone convicted of a powder cocaine offense would receive. But the ruling does give judges who want to lower a sentence here or there the leeway to do so."
Calling the court decision a "minor fix," U.S. District Judge Reggie B. Walton of Washington, said, "The ultimate fix has to be done by Congress." Last month, Walton endorsed retroactive easing of the guidelines on behalf of the Criminal Law Committee of the federal judiciary.
In previous years, the sentencing commission reduced penalties for crimes involving marijuana, LSD and OxyContin, which are primarily committed by whites, and made those decisions retroactive.