The Supreme Court struck down a key part of President Obama’s health-care law Monday, ruling that family-owned businesses do not have to offer their employees contraceptive coverage that conflicts with the owners’ religious beliefs.

The decision deeply split the court, not only on its holding that the federal Religious Freedom Restoration Act (RFRA) protects some businesses from offering contraceptive coverage but also on how broadly the ruling will apply to other challenges in which businesses say laws impose on their religious beliefs.

“Our decision in these cases is concerned solely with the contraceptive mandate,” Justice Samuel A. Alito Jr. wrote for his conservative colleagues. “Our decision should not be understood to hold that an insurance coverage mandate must necessarily fall if it conflicts with an employer’s religious beliefs.”

But Justice Ruth Bader Ginsburg called it a “decision of startling breadth.”

“Suppose an employer’s sincerely held religious belief is offended by health coverage of vaccines, or paying the minimum wage or according women equal pay for substantially similar work?” Ginsburg asked in a strongly worded dissent joined by her three liberal colleagues.

White House press secretary Josh Earnest said Obama thinks the decision “jeopardizes” the health of women. “We believe that the owners of for-profit companies should not be allowed to assert their personal religious views to deny their employees federally mandated benefits,” Earnest said.

He added that the White House “will work with Congress to make sure that any women affected by this decision will still have the same coverage of vital health services as everyone else.”

A senior White House official said that effort would not include an attempt to amend the RFRA, “which has served an important role in protecting religious freedom.”

The requirement in the Affordable Care Act (ACA) that most businesses provide their employees with health-care coverage that includes the full range of contraceptives approved by the Food and Drug Administration has been under legal attack across the country.

Some businesses object to offering contraception at all, while others, like the companies that brought the challenge to the Supreme Court, say offering certain types of birth control, such as intrauterine devices, make them complicit in abortion.

“This is a landmark decision for religious freedom,” said Lori Windham, senior counsel for the Becket Fund for Religious Liberty, which has played a leading role in representing challengers. “The Supreme Court recognized that Americans do not lose their religious freedom when they run a family business.”

The decision came on the last day of the Supreme Court’s term and stood in contrast to a series of earlier rulings in which the court chose a narrow outcome to achieve broad agreement among the justices.

Alito said that his opinion was “very specific” as well. He said it applied specifically to “closely held” companies, which are often family-owned or have a small number of shareholders who tend to hold on to their stock.

And he said the Obama administration could make sure that female workers got the coverage by simply paying for it itself.

Alternatively, he said, the government could give businesses objecting on religious grounds an accommodation like the one provided for religiously oriented not-for-profit corporations (which is also under legal challenge). Those entities can certify their objections and have the group insurer or third-party administrator take on the responsibility of paying for the birth control.

In interpreting the RFRA, the court was considering a 1993 law that gives even broader protections to the exercise of religion than those found in the Constitution. The law prohibits the federal government from imposing a “substantial ­burden” on a person’s exercise of religion, unless there is a “compelling governmental interest” and the measure is the least-restrictive means of achieving the interest.

Companies’ religious rights

The challenges came from two companies. Hobby Lobby is an arts-and-crafts chain that co-founder David Green has said is run on biblical principles. It has grown from a single store, opened in Oklahoma City in 1972, to more than 500 stores nationwide and a workforce of more than 13,000 people of a wide variety of faiths.

The other challenger was Conestoga Wood Specialties, a Pennsylvania cabinetmaking company owned by a Mennonite family, which employs about 950 people.

Alito — joined by Chief Justice John G. Roberts Jr. and Justices Antonin Scalia, Anthony M. Kennedy and Clarence Thomas — decided for the first time that RFRA covers for-profit corporations as well as individuals.

“A corporation is simply a form of organization used by human beings to achieve desired ends,” he wrote. “When rights, whether constitutional or statutory, are extended to corporations, the purpose is to protect the rights of these people.”

The majority said the holding was restricted to closely held corporations controlled by individuals with “sincerely held religious beliefs.”

In this case, the companies’ owners say that four of the 20 contraceptives approved by the FDA work after an egg has been fertilized and thus are abortifacients. While many, if not most, doctors and scientists disagree, Alito said the point is that the owners believe offering such services — such as the morning-after pill and IUDs — violates their religious faiths.

But regulations adopted by the Department of Health and Human Services require all to be offered, and the companies face fines if they do not comply — as much as $1.3 million a day for Hobby Lobby.

The other alternative would be to not offer their employees health insurance, Alito said.

“We doubt that the Congress that enacted RFRA — or, for that matter, ACA — would have believed it a tolerable result to put family-run businesses to the choice of violating their sincerely held religious beliefs or making all of their employees lose their existing healthcare plans,” Alito wrote.

Kennedy wrote separately to say that the opinion he joined “does not have the breadth and sweep ascribed to it” by Ginsburg’s “respectful and powerful dissent.”

He said the government may accommodate female workers whose employers withhold certain contraceptive methods “without imposition of a whole new program or burden on the government.”

Advocates noted that the accommodation being offered to religious-oriented nonprofits is being challenged in lower courts and that future administrations could decide to do away with it. Moreover, said Marcia D. Greenberger, co-president of the National Women’s Law Center, the move segregates contraception from other preventive health care.

“The more it’s segregated, the more it’s treated in a different fashion, the more it becomes not like other health care and vulnerable to these political attacks,” she said.

Ginsburg’s dissent

Ginsburg said the majority did not provide a limitation to its “ ‘let the government pay’ alternative.” And she said the accommodation the administration offers religious nonprofits makes sense only for them, because they are a “community of believers,” not the diverse collection of Americans that make up a company’s workforce.

Moreover, Ginsburg said, the majority’s reasoning undermines its attempts to limit the scope of the decision.

“Although the court attempts to cabin its language to closely held corporations, its logic extends to corporations of any size, public or private,” she wrote. “Little doubt that RFRA claims will proliferate, for the court’s expansive notion of corporate personhood — combined with its other errors in construing RFRA — invites for-profit entities to seek religion-based exemptions from regulations they deem offensive to their faith.”

Ginsburg questioned whether that could include medical treatments such as blood transfusions or vaccinations, or whether companies might seek relief from having to comply with laws outlawing discrimination, if the owners’ religious beliefs could be invoked.

Alito responded that the government has compelling reasons to make sure Americans are immunized. And he discounted Ginsburg’s worry that “discrimination in hiring, for example on the basis of race, might be cloaked as religious practice to escape legal sanction. Our decision today provides no such shield.”

Ginsburg’s dissent was joined in total by Justice Sonia Sotomayor and in part by Justices Stephen G. Breyer and Elena Kagan. The latter two said it was unnecessary to decide now whether for-profit companies or their owners may bring RFRA challenges.

The Greens said they would continue to provide 16 of the 20 FDA-approved contraceptives under the mandate and were “overjoyed” by the Supreme Court’s decision.

“Today the nation’s highest court has re-affirmed the vital importance of religious liberty as one of our country’s founding principles,” Barbara Green, David Green’s wife and co-founder of Hobby Lobby, said in a statement.

It is hard to know how many women could be affected by the ruling. According to a Kaiser Family Foundation poll, 85 percent of large employers already offered contraception coverage before the ACA required it.

The cases are Burwell v. Hobby Lobby Stores and Conestoga Wood Specialties v. Burwell.

Sandhya Somashekhar contributed to this report.