President Obama on Thursday commuted the sentences of eight people serving lengthy jail time for crack cocaine convictions, part of the administration’s effort to reduce “unduly harsh sentences” and eliminate overcrowding in prisons.

Each of the convicts had served at least 15 years in jail and was sentenced prior to the Fair Sentencing Act, a law passed in 2010 to reduce the disparity between crack and powder cocaine convictions, according to the White House. Under that law, the same individuals would have received shorter prison terms and, in some cases, completed their jail time, Obama said in a statement.

“In several cases, the sentencing judges expressed frustration that the law at the time did not allow them to issue punishments that more appropriately fit the crime,” Obama said. “Commuting the sentences of these eight Americans is an important step toward restoring fundamental ideals of justice and fairness.”

The effort marked the first time Obama has commuted the sentences of a group of people.

Obama called on Congress to make further changes to sentencing laws to “ensure that our taxpayer dollars are spent wisely, and that our justice system keeps its basic promise of equal treatment for all.”

The White House also announced Obama had granted pardons to 13 others, including  four in Virginia. Their offenses including distribution of illegal drugs, wire fraud, money laundering and bank embezzlement.