California Attorney General Xavier Becerra on Thursday filed a legal motion asking a judge to halt the implementation of federal rule changes, announced by the Trump administration last month, that give employers more leeway to opt out of the Affordable Care Act’s contraceptive mandate.

Becerra, along with the attorneys general of Delaware, Maryland, New York and Virginia, filed a request for a preliminary injunction in U.S. District Court for the Northern District of California in San Francisco. The move is part of an ongoing lawsuit the states filed in October, which challenges the federal policy change on the grounds that it is unconstitutional and unlawfully targets women.

The rule change, announced by the U.S. Health and Human Services Department on Oct. 6, allows more employers to cite religious or moral objections if they want to stop providing no-cost contraceptive coverage to workers. The change applies only to employers with self-funded health plans, which are regulated by the federal government. It does not apply to employers with fully funded plans, which are regulated by the state — which in 2014 passed a law mandating employer-based health plans provide free birth control to workers, called the Contraceptive Coverage Equity Act.

In California, about 6.6 million people are in employer self-funded plans, according to the California Health Care Foundation.

“A woman’s birth control and health decisions should be made by a woman in consultation with her doctor — not by her employer and not by politicians,” Becerra said in a statement. “These backwards rules will deny millions of women across the United States access to healthcare, unconstitutionally permitting discrimination against women. ... We will not stand by while the Trump administration continues to disregard the rule of law.”

In California, the federal policy change will likely prompt at least 25 employers to opt out of the birth control mandate, which would impact nearly 55,000 women, Becerra’s office estimates.

If granted, the injunction would prevent the policy from taking place nationwide.

Prior to the policy change, only houses of worship, religiously affiliated nonprofits and some private companies with few shareholders, such as Hobby Lobby, could opt out of providing birth control coverage by seeking an “accommodation” — a workaround in which the health insurer rather than the employer pays for the contraception, but women still get access to birth control.

Under the new rules, those employers can go a step further in restricting birth control coverage by seeking an all-out exemption, which means women in those workplaces, and their dependents, will no longer have contraceptive coverage at all. The new rule also allows publicly traded companies and all nonprofits and universities to take a religious exemption.

Catherine Ho is a San Francisco Chronicle staff writer. Email: cho@sfchronicle.com Twitter: @Cat_Ho