As many as 12,000 people jailed in U.S. federal prisons can seek a reduction in their sentences for crimes related to crack cocaine possession.

A law passed by Congress last year ended the lengthy prison terms tied to possession of the crystallized form of cocaine, which were much harsher than sentences for powdered cocaine possession. Civil rights advocates argued the crack cocaine sentences, initially enacted in the 1980s, were racially motivated. Blacks made up the majority of those convicted of crack-related crimes.

The six-member U.S. Sentencing Commission voted unanimously Thursday that the new law applies to those already serving crack-related convictions.

The inmates must submit a petition to a judge to have their sentences reduced. The Sentencing Commission estimates the average reduction will be 37 months.

The federal Bureau of Prisons estimates the reductions will save more than $200 million in housing costs over the next five years.