Since 2022, residents of St. James Parish, along the heavily industrialized banks of the Mississippi River known as “Cancer Alley,” have used low-cost monitors to measure air pollution.

But a new law in Louisiana makes it illegal to use that data to push for stricter pollution controls or enforcement.

The law requires people to instead buy expensive air-pollution monitors that meet strict Environmental Protection Agency standards, if they’re going to use the data to allege violations of clean air laws. People who don’t comply face penalties of thousands of dollars a day.

Now, community groups are fighting the law, saying in a federal lawsuit filed Thursday against Louisiana that it violates their constitutional right to free speech. The law enables polluting industries “to silence the science,” said Caitlion Hunter, director of research and policy at RISE St. James, which leads the air-monitoring efforts.

The Louisiana law was the first of its kind in the country when it went into effect last year. But Kentucky passed a similar law this year and West Virginia’s legislature debated a version in February, though it did not pass.

The Louisiana Department of Environmental Quality declined to comment. Louisiana Attorney General Liz Murrill did not respond to requests for comment.