As part of a continuing reform of the nation’s drug laws, Attorney General Eric Holder said this week that the Justice Department is expanding a program that will allow President Obama to consider clemency requests from nonviolent drug offenders who were previously ineligible because of sentencing guidelines.

Last week, Mr. Holder responded to prompting from the White House to revamp the rules for commutation and pardon requests. The pool of low-level, nonviolent clemency applicants is expected to jump dramatically as a result.

These long overdue changes reflect Mr. Obama’s desire to shrink the federal prison population, which is clogged with an estimated half-million nonviolent drug offenders. It also acknowledges the unfairness of the system.

Because of mandatory minimum sentencing guidelines, offenders convicted of nonviolent drug crimes faced far more years behind bars than judges and even many prosecutors would have preferred. Such sentences contribute to the perception that justice is arbitrary — a perception that, if allowed to stand, undermines the criminal justice system.

It is too early to tell how many nonviolent drug offenders will apply for clemency, or how many will receive a response saying their days in federal prison are almost over. The cost to taxpayers of holding them years beyond what would have been fair has been steep. The cost of tolerating such a flawed system for so long has been steeper.

First Published April 23, 2014, 1:20 a.m.