President Barack Obama has commuted the sentences of eight individuals convicted of crack cocaine offenses.

In a statement, Obama said the commutation “is an important step toward restoring fundamental ideals of justice and fairness” and noted that he signed legislation in 2010 to narrow the disparity between penalties for crimes related to powder and crack cocaine.

Obama has pushed to change criminal justice policy to correct what his administration calls unfairness in sentencing and to keep down the cost of lengthy incarcerations for non-violent crimes.

“If they had been sentenced under the current law, many of them would have already served their time and paid their debt to society,” he said of inmates sentenced before the passage of the Fair Sentencing Act. “Instead, because of a disparity in the law that is now recognized as unjust, they remain in prison, separated from their families and their communities, at a cost of millions of taxpayer dollars each year.”

White House Press Secretary Jay Carney is asked Thursday about the administration's decision to shorten the sentences of a group of individuals convicted of crack cocaine offenses.

Obama also called on Congress to pass pending legislation that would make the Fair Sentencing Act retroactive for some offenders.

Each of the eight offenders has served over 15 years in prison for the drug crimes.

One of the individuals, Clarence Aaron of Mobile, Ala., was convicted in the early 1990s at the age of 22 for conspiracy to distribute cocaine. Aaron's lawyer Margaret Love told NBC News that Aaron was "overcome" with emotion and that he will head to a halfway house in his hometown in coming weeks.

The president also pardoned thirteen other individuals for crimes ranging from drug offenses to money laundering to theft.

The NAACP Legal Defense Fund praised the decision in a statement.

"The president's ability to commute sentences is an extraordinary power, and his decision to exercise that power in these cases sends a powerful signal that the White House is committed to reducing mass incarceration and working to restore fairness to the criminal justice system," said Sherrilyn A. Ifill, the group's president.

The Obama administration has been vocal about the need to reduce the sentencing disparity and to avoid triggering mandatory minimum sentences in drug cases.

In August, Attorney General Eric Holder directed federal prosecutors not to report the amount of drugs involved in an arrest if it would trigger mandatory minimums. The order applied to non-violent offenders who have no ties to drug cartels or gangs and who did not sell to children.

The attorney general said too many Americans get long prison sentences that don't fit the crime. "With an outsized, unnecessarily large prison population, we need to ensure that incarceration is used to punish, deter, and rehabilitate -- not merely to warehouse and forget."

The number of inmates in federal prison, roughly 219,000, is eight times what it was 30 years ago, and 40 percent over capacity. Nearly half are there for drug related crimes and roughly one-fourth of them were low-level offenders.

NBC's Shawna Thomas and Pete Williams contributed to this report.