Democratic attorneys general are making a renewed push to challenge the latest regulation governing the Affordable Care Act's marketplaces.

In a lawsuit filed Friday, the AGs of 21 states, as well as Pennsylvania Gov. Josh Shapiro, argue that the rule, which establishes key policies for the 2027 plan year, will make ACA plans more expensive and harder to access in their states.

The coalition of officials similarly challenged the 2025 rule governing the 2026 plan year, and earlier this summer, a federal court vacated several provisions of that rule that were in question. The AGs say the 2027 ACA rule reinstates a number of the elements that were blocked in court.

In addition, the regulation "adds new changes that further undermine the ACA," such as an expansion of catastrophic health plans that goes beyond limits established in the law, per the lawsuit.

The AGs also argue that the rule allows catastrophic- and bronze-tier plans to circumvent the out-of-pocket maximums established by law. Further, the changes were adopted "without adequate explanation or a meaningful response" to comments from the coalition, which would be considered "arbitrary and capricious" under the Administrative Procedure Act, according to the suit.

The lawsuit is led by New Jersey Attorney General Jennifer Davenport and California AG Rob Bonta.

"The Trump Administration’s policies have already caused over a million Americans to lose coverage. If these additional changes aren’t stopped, the situation will only get worse,” Davenport said in a press release.

The state officials note that the Department of Health and Human Services estimates that the rule would lead to 2 million people losing coverage in 2027, growing to 5 million by 2030.

"We are returning to court to challenge these unlawful changes," Bonta said in a statement. "At a time when families are already facing rising costs, they cannot afford to pay more for coverage that gives them less."

HHS is currently appealing the court's decision to vacate key elements of the 2025 program integrity rule.