WASHINGTON — The Supreme Court ruled on Monday that requiring family-owned corporations to pay for insurance coverage for contraception under the Affordable Care Act violated a federal law protecting religious freedom. It was, a dissent said, “a decision of startling breadth.”

The 5-to-4 ruling, which applied to two companies owned by Christian families, opened the door to many challenges from corporations over laws that they claim violate their religious liberty.

The decision, issued on the last day of the term, reflected what appears to be a key characteristic of the court under Chief Justice John G. Roberts Jr. — an inclination toward nominally incremental rulings with vast potential for great change.