WASHINGTON (AP) — Attorney General Merrick Garland moved Friday to end sentencing disparities that have imposed harsher penalties for different forms of cocaine and worsened racial inequity in the U.S. justice system.

For decades federal law has imposed harsher sentences for crack cocaine even though it isn’t scientifically different from powder cocaine, creating “unwarranted racial disparities,” Garland wrote in a memo. “They are two forms of the same drug, with powder readily convertible into crack cocaine.”

With changes to the law stalled in Congress, Garland instructed prosecutors in non-violent, low-level cases to file charges that avoid the mandatory minimum sentences that are triggered for smaller amounts of rock cocaine.

Civil rights leaders and criminal justice reform advocates applauded the changes, though they said the changes won’t be permanent without action from Congress.

Rev. Al Sharpton led marches in the 1990s against the laws he called “unfair and racially tinged” and applauded the Justice Department direction that takes effect within 30 days.

“This was not only a major prosecutorial and sentencing decision – it is a major civil rights decision,” he said in a statement. “The racial disparities of this policy have ruined homes and futures for over a generation.”

At one point, federal law treated a single gram of crack the same as 100 grams of powder cocaine. Congress shrunk that gap in 2010 but did not completely close it. A bill to end the disparity passed the House last year, but stalled in the Senate.

“This has been one of the policies that has sent thousands and thousands of predominantly Black men to the federal prison system,” said Janos Marton, vice-president of political strategy with the group Dream.org. “And that’s been devastating for communities and for families.”

While he welcomed the change in prosecution practices, he pointed out that unless Congress acts, it could be temporary. The bill that passed the House with bipartisan support last year would also be retroactive to apply to people already convicted under the law passed in 1986.

The Black incarceration rate in America exploded after the Anti-Drug Abuse Act of 1986 it went into effect. It went from about 600 per 100,000 people in 1970 to 1,808 in 2000. In the same timespan, the rate for the Latino population grew from 208 per 100,000 people to 615, while the white incarceration rate grew from 103 per 100,000 people to 242.

The mandatory-minimum policies came as the use of illicit drugs, including crack cocaine in the late 1980s, was accompanied by an alarming spike in homicides and other violent crimes nationwide.

The act was passed shortly after an NBA draftee died of a cocaine-induced heart attack. It imposed mandatory federal sentences of 20 years to life in prison for violating drug laws and made sentences for possession and sale of crack rocks harsher than those for powder cocaine.

Friday’s announcement reflects the ways that years of advocacy have pushed a shift away from the war on drugs tactics that took a heavy toll on marginalized groups and drove up the nation’s incarceration rates without an accompanying investment in other services to rebuild communities, said Rashad Robinson, president Color Of Change.

“It is a recognition these laws were intended to target Black people and Black communities and were never intended to give communities the type of support and investments they need,” he said.