WASHINGTON (AP) — The Justice Department said Tuesday that a proposal that would result in shorter prison sentences for drug criminals should apply to some, but not all, drug felons who are currently behind bars.

A proposal adopted in April by the U.S. Sentencing Commission, which establishes sentencing policies, would lower the sentencing levels used by judges in sentencing drug traffickers. The commission estimated at the time that about 70 percent of federal drug trafficking defendants would qualify for reduced sentences and that the change, if implemented, would help cut the federal prison population by more than 6,500 inmates over the next five years.