vaccine mandate protester
© CNBCA lone protester stands outside the U.S. Supreme Court as it hears arguments against the Biden administration's nationwide vaccine-or-testing COVID-19 mandates, in Washington, January 7, 2022.
The mandate required that workers at businesses with 100 or more employees must get vaccinated or submit a negative Covid test weekly to enter the workplace. It also required unvaccinated workers to wear masks indoors at work.

OSHA, which polices workplace safety for the Labor Department, issued the mandates under its emergency power established by Congress. OSHA can shortcut the normal rulemaking process, which can take years, if the Labor secretary determines a new workplace safety standard is necessary to protect workers from a grave danger.

The Biden administration argued before the high court Friday that the rules were necessary to address the "grave danger" posed by the Covid pandemic. Liberal justices, clearly sympathetic to the government's position, highlighted the devastating death toll from the pandemic and the unprecedented wave of infection rolling across the nation due to the omicron variant.

But the court's 6-3 conservative majority expressed deep skepticism about the federal government's move.

Chief Justice John Roberts, who was appointed by President George W. Bush, said during arguments that he thinks it's hard to argue that the 1970 law governing OSHA "gives free reign to the agencies to enact such broad regulation."

The vaccine-or-test rules faced a raft of lawsuits from 27 states with Republican attorneys general or governors, private businesses, religious groups and national industry groups such as the National Retail Federation, the American Trucking Associations and the National Federation of Independent Business.

The mandates were the most expansive use of power by the federal government to protect workers from Covid since the pandemic began.