“The mandate is aimed directly at protecting the unvaccinated from their own choices,” she wrote. “Vaccines are freely available, and unvaccinated people may choose to protect themselves at any time.”

In the Supreme Court case, National Federation of Independent Business v. Department of Labor, No. 21A244, the challengers argued that the regulation did not address a workplace issue and so exceeded the agency’s lawful authority. “Covid-19 is not an occupational danger that OSHA may regulate,” lawyers for Ohio and 26 other states told the justices in a recent brief.

They added that agencies seeking to issue regulations on “major questions” with broad economic or political implications must have clear congressional authorization.

The second case, Biden v. Missouri, No. 21A240, concerns a regulation issued in November requiring health care workers at facilities that receive federal money under the Medicare and Medicaid programs to be vaccinated against the coronavirus unless they qualify for a medical or religious exemption.

States led by Republican officials challenged the regulation, obtaining injunctions against it covering about half of the nation. Two federal appeals courts, in New Orleans and St. Louis, refused to stay those injunctions while appeals moved forward.

A third federal appeals court, in Atlanta, sided with the Biden administration. “Health care workers have long been required to obtain inoculations for infectious diseases, such as measles, rubella, mumps and others,” Judges Robin S. Rosenbaum and Jill A. Pryor wrote for a divided three-judge panel, “because required vaccination is a common-sense measure designed to prevent health care workers, whose job it is to improve patients’ health, from making them sicker.”

The Biden administration argued that a federal statute gave it broad authority to impose regulations concerning the health and safety of patients at facilities that receive federal money. The statute gives the secretary of the Department of Health and Human Services the general power to issue regulations to ensure the “efficient administration” of the Medicare and Medicaid programs, and parts of the statute concerning various kinds of facilities generally also authorize the secretary to impose requirement to protect the health and safety of patients.