The Trump administration is taking aim at states that have legalized marijuana. On Thursday, U.S. Attorney General Jeff Sessions announced he is rescinding an Obama-era policy that discouraged prosecutors from enforcing federal marijuana laws in states that have legalized its sale for recreational use.

Massachusetts is one of eight states that has voted to legalize recreational use of marijuana, and several more are expected to pass similar laws this year.

Grant Smith, the deputy director of the Office of National Affairs for the Drug Policy Alliance, says Sessions’ action undermines state-level reforms around the country.

“It has a chilling effect in terms of the ability for states to move forward with marijuana law reforms that have dramatically cut arrests, and with that, have helped to reduce racial disparities with the marijuana arrests we’ve been seeing,” he laments.

The Massachusetts Cannabis Control Commission says it will proceed with plans to begin marijuana sale for recreational use, despite the announcement. Before this week’s action, Sessions has voiced concerns about marijuana use and blames legalization for challenging law enforcement and encouraging drug trafficking.

Twenty-nine states now have laws allowing the sale of medical marijuana. But Smith notes that the attorney general’s action should not affect clinics or patients.

“There’s a rider that’s still currently in effect, that was passed by Congress, that prohibits the Department of Justice from spending federal funds to interfere with the implementation of state medical-marijuana laws,” he says.

In May, Sessions sent a letter to Congress asking for that rider to be removed, but the provision has strong, bipartisan support.

And Smith points out that public support for ending marijuana prohibition is strong and growing.

“The latest Gallup poll shows that 64 percent of Americans support making marijuana use legal,” he adds. “And I don’t think the voters are going to be swayed by Attorney General Sessions’ perspective on this.”

He also points out that states that have legalized cannabis have benefited through increased tax revenue from sales.