WASHINGTON — In a 5-4 decision, the Supreme Court on Tuesday declared as probably unconstitutional a California law that required religiously affiliated pregnancy centers to inform clients about the availability of state-funded services for terminating a pregnancy.

The decision was a victory for a religious group representing church-run crisis pregnancy centers that claimed the requirement violated the First Amendment's guarantee of free expression by forcing them to convey a message they strongly oppose.

California's Reproductive FACT Act required licensed medical centers to post a notice advising women about the availability of state-funded programs that provide family planning services including contraceptives and abortion. Nonmedical facilities are required to display notices explaining that they are not licensed and cannot provide medical services. The court struck down the part of the law pertaining to unlicensed centers.

Justice Clarence Thomas said in his majority opinion said the centers "are likely to succeed" in their constitutional challenge to the law.

Justice Stephen Breyer, writing for four liberal dissenters, said among the reasons the law should be upheld is that the high court has previously upheld state laws requiring doctors to tell women seeking abortions about adoption services. "After all, the law must be evenhanded," Breyer said.

House Minority Leader Nancy Pelosi, D-Calif., said the ruling "is a grave step backwards in our nation’s fight to protect and advance the rights of women and opens the door for anti-choice activists to deceive and prey on vulnerable women seeking complete, accurate and unbiased information critical to their health and wellbeing."

The religiously affiliated centers — around 300 in the state — support childbirth by encouraging women to opt for parenting or adoption. They provide vitamins, diapers, and baby clothes. Some offer ultrasound images. Forcing them to post the notices, they argued, amounted to government-compelled speech.

In defending the law, the state said about half of California's 700,000 pregnancies a year are unintended and that many women with low incomes aren't aware of publicly funded health care options. The law was designed, said California Attorney General Xavier Becerra, "to reach an audience in need of information at a critical moment," given that "late abortions may be less safe, less desirable, and more burdensome to obtain."

State legislators who pushed for the law said some pregnancy centers give misleading information about the risks of abortion, pretend to be medical clinics, or intimidate their clients.

Lower courts were divided about whether such notice requirements violate free speech. The Ninth Circuit Court of Appeals upheld the California law, but similar requirements in other states and cities have been declared unconstitutional.

Many of the nation's courts have, however, upheld laws in 29 states that require doctors to provide various kinds of information to patients before performing abortions. The states say the laws are important for obtaining informed consent. But women's groups say the information is often inaccurate about the risks.