Marijuana legalization does a lot of things, but one thing it doesn’t do is stop racial disparities in the criminal justice system — even with marijuana arrests.

In a recent report by the Drug Policy Alliance, the pro-legalization group documented the effects of marijuana legalization in several states. As expected, marijuana arrests are down dramatically in legal pot states. But arrests remain for, say, possession by people who are under the legal age of 21, unlicensed sales, and public consumption.

Drug Policy Alliance

Things get a little more complicated, though, when you break the data down by race. Arrests have declined for all racial groups since legalization. But that hasn’t halted racial disparities.

Both black and white people are much less likely to be arrested over marijuana, but black people are still much more likely to be arrested for pot in comparison to white people.

Alaska legalized marijuana in 2014, although it did not start sales until 2016. In the state, white and black arrest rates fell by nearly 99 percent and more than 93 percent, respectively, between 2012 and 2016. But black people were arrested for marijuana at a rate of 17.7 per 100,000 in 2016, while white people were arrested at a rate of 1.8 per 100,000 — about 10 times less.

Drug Policy Alliance

Washington, DC, decriminalized marijuana in 2014, then legalized possession and growing but not sales in a voter-approved ballot initiative that same year. For possession, arrest rates between 2010 and 2016 dropped by more than 99 percent for black people and almost 99 percent for white people. But, again, racial disparities remained: Black people were arrested for possession at a rate of 8 per 100,000 people in 2016, while white people were arrested at a rate of 2 per 100,000 — four times less.

Drug Policy Alliance

This is similar to what we saw in Colorado, one of the first two states to legalize pot in 2012. A 2016 report from the Colorado Department of Public Safety found, “The decrease in the number of marijuana arrests by race is the greatest for White arrestees (‐51%) compared to Hispanics (‐33%) and African‐Americans (‐25%). The marijuana arrest rate for Whites and Hispanics is comparable, but the marijuana arrest rate for African‐Americans is almost three times that of Whites (348/100,000 for Blacks and 123/100,000 for Whites).”

This is still progress for marijuana legalization advocates, since fewer people of all races are arrested for cannabis in the end.

But the findings also show the persistence of racial disparities in the criminal justice system.

The disparities are not explained by differences in black and white marijuana use rates. Surveys show black and white Americans use cannabis at similar levels.

Instead, there seems to be some level of bias built into the criminal justice system. Perhaps it’s individual racial biases among police officers. Maybe it’s how police are disproportionately deployed in minority communities, purportedly because they have higher levels of crime.

Then there are socioeconomic disparities that may drive some groups to, for example, more frequently use and sell drugs outdoors instead of indoors. All of these factors and others are likely working together to maintain racial disparities in the criminal justice system.

For more on marijuana legalization, read Vox’s explainer.