Update, March 18: The Department of Health and Human Services filed a stay today on the SUNSET rule, according to Law360.

A Trump administration rule finalized the day before President Biden’s inauguration is a “ticking time bomb” that could invalidate thousands of other rules, including protections for the elderly, creating “incalculable costs and chaos,” according to a lawsuit filed last week against the Department of Health and Human Services.

The Securing Updated and Necessary Statutory Evaluations Timely (SUNSET) rule — proposed the day after the November election and finalized the day before Biden’s inauguration — requires HHS to review all 18,000 existing agency regulations before an automatic expiration date kicks in. The agency has said that to do so would require redirecting resources away from the pandemic.

“The SUNSET rule sets off a ‘ticking time bomb’ that will eliminate thousands of existing regulations that govern our healthcare system, food safety protocols, public health measures, social services, and so much more,” according to the plaintiffs. “HHS’s SUNSET Rule is ill-conceived, impractical and unlawful. Unless it is immediately halted, millions of Americans, including more than 36 million children, will be hurt by the resulting regulatory chaos, uncertainty, and elimination of key protections.”

The complaint, filed in the U.S. District Court for the Northern District of California, seeks to vacate the “unlawful SUNSET rule and prevent the substantial harm” it will cause healthcare providers, business and nonprofit organizations, individuals and public health. The suit is being brought by Santa Clara County, the California Tribal Families Coalition, the National Association of Pediatric Nurse Practitioners, the American Lung Association, the Center for Science in the Public Interest and the Natural Resources Defense Council.

The rule would eliminate nearly all HHS regulations beginning in five years, including regulations issued by the Centers for Disease Control and Prevention, the Food and Drug Administration and the National Institutes of Health. Without review, about 17,200 regulations automatically will be eliminated in 2026, with additional regulations expiring later, according to the Natural Resources Defense Council.

The suit states that the rule will affect regulations governing health insurance, pharmaceuticals and vaccines, mental health treatment, Medicare, Medicaid, public health emergency prevention and preparedness, food safety, and protections for the elderly and children, among other areas.

According to the SUNSET rule, any regulation issued by HHS will cease to be effective 10 years after it is issued. In proposing the rule last year, HHS said it would “sunset burdensome regulations unless their necessity is publicly demonstrated to the American people.”

HHS estimated that it will need to perform over 3,400 reviews over the next five years. That will necessitate increasing its pace of review 20-fold to keep existing rules on the books in 2026. The effort also will come at a “significant cost to society,” as HHS and its sub-agencies redirect resources away from the pandemic, the agency said.

The complaint states that the SUNSET Rule violates the Administrative Procedure Act and the Regulatory Flexibility Act by failing to name which regulations will expire, provided an insufficient notice and comment period, and unlawfully refused to consult with Indian tribes.

Because the rule was filed so late in the Trump administration, Congress could eliminate it through the Congressional Review Act. HHS also could decide “to stay the rule and suspend its implementation its effective date indefinitely while the litigation is pending,” according to an NPR article.