WASHINGTON (AP) — New Trump administration rules that give millions of people a shorter timeframe to sign up for the Affordable Care Act’s health care coverage are facing a legal challenge from Democratic mayors around the country.

The rules, rolled out last month, reverse a Biden-era effort to expand access to the Affordable Care Act’s health insurance, commonly called “Obamacare” or the ACA. The previous Democratic administration expanded the enrollment window for the coverage, which led to record enrollment.

The Department of Health and Human Services rolled out a series of new restrictions for Obamacare late last month, just as Congress was weighing a major bill that will decrease enrollment in the health care program that Republican President Donald Trump has scorned for years. As many as 2 million people — nearly 10% — are expected to lose coverage from the health department’s new rules.

The mayors of Baltimore, Chicago and Columbus, Ohio sued the federal health department on Tuesday over the rules, saying they will result in more uninsured residents and overburden city services.