The Supreme Court ruled on Thursday that recent changes to penalties for crimes that involve crack cocaine, which make sentences more lenient, can be applied retroactively.

The court ruled that Congress intended the lighter sentences it created for crack-cocaine offenders under the Fair Sentencing Act to begin immediately, even for those whose crimes were committed before the law was signed, The Wall Street Journal reports.

While powder and crack cocaine are two forms of the same drug, until recently, a drug dealer who sold crack cocaine was subject to the same sentence as a dealer who sold 100 times as much powder cocaine.

The Fair Sentencing Act, enacted in 2010, reduced the disparity from 100 to 1 to 18 to 1, for people who committed their crimes after the law took effect. As a result, many defendants who are caught with small amounts of crack are no longer subject to mandatory prison sentences of five to 10 years. Those convicted of crack-cocaine crimes tend to be black, while those convicted of powder-cocaine offenses tend to be white, The Washington Post notes.

The two cases before the court centered on whether the new sentencing guidelines also apply to those who committed crimes before the law took effect, but who were not sentenced until afterwards.

In one case heard by the court, a man who pleaded guilty in June 2010 to possessing 5.5 grams of crack cocaine in 2008 with the intent to distribute it was subject to a mandatory minimum sentence of 10 years. Under the new law, the mandatory sentence would not have been given for fewer than 28 grams, and the man probably would have received a sentence of three or four years.

In the second case, a man was convicted in 2009 of selling 53 grams of crack cocaine, and was sentenced under the old law in December 2010, after the new law had taken effect.