The US Supreme Court delivered a blow to President Joe Biden on Thursday, blocking his Covid vaccination-or-test mandate for large businesses.
At the same time, the nation's highest court allowed a vaccination mandate for health care workers at facilities receiving federal funding to go ahead.
After months of public appeals to Americans to get vaccinated against Covid-19, which has killed more than 845,000 people in the United States, Biden announced in September that he was making vaccinations compulsory at companies that employ 100 workers or more.
Unvaccinated employees would have to present weekly negative tests and wear face masks at work.
The Occupational Safety and Health Administration (OSHA), a federal agency, gave businesses until February 9 to be in compliance with the rules or face the possibility of fines.
But the Supreme Court's six conservative justices ruled the mandate would represent a "significant encroachment into the lives -- and health -- of a vast number of employees."
"Although Congress has indisputably given OSHA the power to regulate occupational dangers, it has not given that agency the power to regulate public health more broadly," they said.
"Requiring the vaccination of 84 million Americans, selected simply because they work for employers with more than 100 employees, certainly falls in the latter category," they added.
The three liberal justices dissented.
The vaccination mandate for health care workers at facilities receiving federal funding was approved in a 5-4 vote, with two conservatives -- Chief Justice John Roberts and Justice Brett Kavanaugh -- joining the liberals.
"Ensuring that providers take steps to avoid transmitting a dangerous virus to their patients is consistent with the fundamental principle of the medical profession: first, do no harm," they said in the majority opinion.
Vaccination has become a politically polarizing issue in the United States, where 62 percent of the population are vaccinated.
A coalition of 26 business associations had filed suit against the OSHA regulations and several Republican-led states had challenged the mandate for health care workers.
Some Republican lawmakers cheered the high court striking down business mandates.
"Today's Supreme Court ruling sends a clear message: Biden is not a king & his gross overreaches of federal power will not be tolerated," Senator Rick Scott tweeted.
"I had COVID & got the vaccine, but I will NEVER support a vaccine mandate that bullies hardworking Americans & kills jobs."