The Supreme Court on Thursday blocked the Biden administration’s Covid-19 vaccine-or-testing rules for large private employers, upending the government’s most aggressive effort to combat the pandemic in the workplace. The high court, however, did give the administration more latitude in the healthcare industry, allowing it to impose a vaccine mandate for more than 10 million healthcare workers whose facilities participate in Medicare and Medicaid, a holding that leaves one part of the president’s Covid-19 playbook in place. The private-employer requirements, for businesses with 100 or more employees, would have applied to an estimated 84 million workers. The court’s conservative majority, in an unsigned opinion, said the Biden administration likely didn’t have the unilateral power to impose a mandate that employers ensure their workers were vaccinated or tested every week for Covid-19. Three liberal justices dissented. In allowing the vaccine mandate for healthcare workers, conservatives Chief Justice John Roberts and Justice Brett Kavanaugh joined the three liberals to form a 5-4 majority, allowing that requirement to take effect nationwide.

Technically, the Supreme Court wasn’t considering the full merits of the administration’s mandates. Instead, the justices heard the cases on an emergency basis to decide whether the regulations could go into effect right now while more detailed litigation continued in the lower courts. A conservative high court skeptical of sweeping federal power also blocked the administration last August from continuing with a ban on evictions during the pandemic. The court has been more accepting of Covid-19 mitigation measures adopted at the state and local levels, including mandates requiring healthcare workers and college students to be vaccinated.

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