Washington, United States (AFP) — The US attorney general ordered justice officials to treat drug offenders equally in powder cocaine and crack cocaine cases, after decades of disparities saw African Americans jailed more often and longer than whites.

In a directive to the Department of Justice, Merrick Garland said there was no reason to apply harsher penalties for crack offenses.

"The crack/powder disparity is simply not supported by science, as there are no significant pharmacological differences between the drugs" said the directive.

When crack, a cocaine derivative, swept through the United States in the 1980s and 1990s, Congress passed a law — crafted by then-senator and now President Joe Biden — setting harsher penalties for possession and dealing than those for powder cocaine.

The law recommended up to five years in prison for possession of 500 grams of cocaine, but only five grams of crack, justifying it by the more intense impact of crack, according to The Sentencing Project.

In addition, crack possession carried a mandatory prison sentence for the first offense involving more than five grams.

At the time crack was most common in poorer and African American communities, while powder cocaine was more widespread among whites and the wealthy.

The result was mass incarceration of Black people, often for very lengthy sentences, during the crack epidemic, swelling jail populations for long periods.

The consequences still echo through the prison system and Black communities, despite a 2010 law that eliminated the mandatory sentencing requirements for crack and changed the ratio to 18-to-1.

Though less harsh, it still treated crack use as far worse than powder cocaine.

A law signed by then president Donald Trump in 2018 allowed crack offenders to appeal based on the disparity in sentencing for the two drugs.

It has led to more than 4,500 people seeing their sentences reduced, according to an August 2022 report by the US Sentencing Commission.

But the memo from Garland, a Biden appointee, said "the crack/powder sentencing differential is still responsible for unwarranted racial disparities in sentencing."

"The higher penalties for crack cocaine offenses are not necessary to achieve (and actually undermine) our law enforcement priorities," it said.

Garland said the Biden administration supports proposed legislation to change the sentencing laws in Congress, the EQUAL Act.

The act was submitted in January 2021 but has not advanced.