resident Obama waved to reporters last month as he left the White House before boarding the Marine One helicopter on the South Lawn. (Photo by Chip Somodevilla/Getty Images)

President Obama, who has stepped up his campaign this year to overhaul the nation's criminal justice system, commuted the sentences of 22 drug offenders Tuesday.

More than a year after the Justice Department launched an initiative aimed at granting clemency to nonviolent offenders, the effort has gotten off to a slow start,  In December 2013 Obama commuted the sentences of eight people as part of the effort, all of whom were serving lengthy prison sentences for crack cocaine offenses.

In a blog post outlining the reasoning behind the Tuesday pardons, White House counsel Neil Eggleston noted that under current sentencing guidelines many of the individuals receiving clemency would have already served their time in prison.

"Because many were convicted under an outdated sentencing regime, they served years — in some cases more than a decade — longer than individuals convicted today of the same crime," Eggleston said, adding that the commutations "underscore the president’s commitment to using all the tools at his disposal to bring greater fairness and equity to our justice system."

[READ: Clemency effort relies on an army of pro-bono lawyers]

The individuals receiving commutations Tuesday include men and women from California to Kansas to Florida, who were serving extended sentences for the possession, sale and distribution of substances including methamphetamine, marijuana, crack cocaine and base cocaine. The president wrote a letter to each of the 22 individuals -- all of whom but one now have sentences commuted to expire July 28 -- urging them to use this chance to rebuild their lives.

"I am granting your application because you have demonstrated the potential to turn your life around.  Now it is up to you to make the most of this opportunity," Obama wrote. "It will not be easy, and you will confront many who doubt people with criminal records can change... But remember that you have the capacity to make good choices."

"I believe in your ability to prove the doubters wrong," the president concluded, "So good luck, and Godspeed."

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