In a decision said to be a “big deal” for voters in a crucial swing state, a federal court on Friday declared that Ohio’s practice of purging millions of registered citizens from its rolls is in violation of national voting laws.

The order reverses a lower court ruling, which favored Secretary of State Jon Husted. In Friday’s opinion (pdf), District Judge George C. Smith declared that “Ohio’s Supplemental Process [for removing voters from the rolls] violates Section 8, subsection (b)(2) of the [National Voter Registration Act (NVRA)].”

Ohio’s “purge” is said to be the most aggressive in the nation, removing more voters over a five-year period than any other state. Since 2011, more than 2 million voters have been purged. According to Husted’s office, from 2011 to 2014, 846,000 were scrapped for infrequent voting and 480,000 for moving.

The Nation columnist Ari Berman recently explained that it “works like this: If a voter misses an election, Ohio sends them a letter making sure their address is still current. If the voter doesn’t respond, Ohio puts them on an inactive list, and if the voter doesn’t vote in the next two elections they are removed from the rolls.”

Smith acknowledges that Husted did take some steps to remedy the registration policy by issuing a new form, but said that the secretary had failed to carry “his burden of showing that is is ‘absolutely clear the allegedly wrongful behavior could not reasonably be expected to recur.'”

Further, he agreed with the plaintiffs’ argument that the “newly-issued form does nothing to correct the fact that Ohio has, for years, been removing voters from the rolls because they failed to respond to forms that are blatantly non-compliant with the NVRA.”

The plaintiffs, which include the A. Philip Randolph Institute, the Northeast Ohio Coalition for the Homeless, and citizen Larry Harmon, argued that purging voters for infrequent voting “has a disparate impact on minority communities” and particularly burdens “poor and illiterate voters [who may be] caught in a purge system which will require them to needlessly re-register.”

Though Husted has alleged that the process is done in a uniform manner, a Reuters investigation found that “the policy appears to be helping Republicans in the state’s largest metropolitan areas.”