• President Joe Biden is betting that his unprecedented coronavirus vaccine mandate will prevail against a flurry of lawsuits aiming to strike it down.
• The legal battle is likely to reach the Supreme Court.
• The vaccination rules are "unprecedented in scope," but are built on an extensive framework of legal public health and safety regulations, an expert told CNBC.

President Joe Biden is betting that his unprecedented coronavirus vaccine mandate will prevail against a flurry of lawsuits aiming to strike it down. The legal battle is expected to reach the Supreme Court.

Biden believes the mandate, which would make businesses with 100 or more employees require their staff to get vaccinated or face regular testing by Jan. 4, will cover about two-thirds of all U.S. workers and hasten the end of the coronavirus pandemic. The White House says legal precedent gives it the authority to act to respond to the "grave danger" posed by the pandemic.

Republican attorneys general in at least 26 states and numerous private businesses and industry groups have sued, arguing that the mandate is an unconstitutional flex of government power over Americans' lives.

The clash marks just the latest example of the deep-seated ideological divisions that have defined the United States' response to the Covid pandemic, where the push to crush the virus has frequently collided with efforts to protect personal liberties.

The vaccination rules are "unprecedented in scope," but are built on an extensive framework of legal public health and safety regulations, said Dorit Reiss, a law professor focusing on vaccine policies at the University of Hastings, California College of the Law.

"We do already have a lot of very aggressive work rules. So it's broader than we've seen in the past, but it's also following a long tradition of regulating the workplace," Reiss said.

Days after the rules were published, the U.S. Court of Appeals for the 5th Circuit, considered one of the most conservative appellate courts in the country, agreed with the Republican AGs to freeze Biden's vaccine mandate pending a review.

The 5th Circuit in Louisiana imposed a court-order stay that delays the mandate from taking effect while the rule is under review. The court said the attorneys general's arguments "give cause to believe there are grave statutory and constitutional issues with the Mandate." All of the lawsuits seeking to overturn the rule were consolidated into one case Tuesday and randomly assigned to the conservative-leaning 6th Circuit Court of Appeals in Cincinnati, Ohio.

David Vladeck, a professor of law at Georgetown University, said there's a "high probability" the case will end up before the Supreme Court, which has grown significantly more conservative after former President Donald Trump nominated three justices to the nine-seat bench.

"There are justices on the court who want to rein in the administrative state and this is a case in which those concerns are likely to come to the fore," Vladeck told CNBC.

Even if it survives the courts, enforcement of the mandate won't begin until early next year. The White House and U.S. Chamber of Commerce are encouraging employers to start enforcing the vax-or-test rules immediately, despite the appellate court's injunction.

Courts and Covid

State and local governments, as well as private businesses, have been sued throughout the pandemic over the wide range of social distancing rules that aimed to dampen the spread of the virus.

Overall, the courts have been mostly deferential to the public health officials imposing the rules, except with regard to restrictions on religious services, Reiss told CNBC.

Examples abound at all levels of the judiciary. Last week, for instance, a federal judge in Texas upheld United Airlines' strict vaccine policy for its employees. In September, another U.S. district judge ruled that a private health-care provider near Cincinnati, Ohio, could require workers to either get inoculated or risk losing their jobs.

Late last month, a federal appeals court approved New York's vaccine mandate for health-care employees. That ruling reversed a lower court's move temporarily blocking the mandate over what it considered to be inadequate religious exemptions.

The U.S. Supreme Court has on multiple occasions denied to hear cases challenging state vaccine rules, including those brought by health-care workers in Maine and students at Indiana University.

The debate over vaccine mandates has drawn attention to a pair of related Supreme Court rulings from the early 20th Century — particularly in the 1905 case Jacobsen v. Massachusetts.

Smallpox precedent

That case centered on a challenge of a smallpox vaccine mandate in Cambridge, Massachusetts, which the city deemed "necessary for the speedy extermination of the disease." The court in a 7-2 ruling sided with the state, holding that the vaccination rule was needed to ensure public health and safety.

The court upheld that ruling 17 years later in Zucht v. King, when it rejected a bid to defy public school vaccination requirements in San Antonio, Texas.

But judges might not be convinced that those cases, which deal with state-imposed rules, will provide the constitutional basis to prop up Biden's much broader federal mandate.

Judge Kurt Engelhardt of the U.S. Court of Appeals for the 5th Circuit, cited Jacobsen and Zucht in his decision last week blocking the mandate from taking effect.

"To mandate that a person receive a vaccine or undergo testing falls squarely within the States' police power," said Engelhardt, an appointee of Trump.

"The Commerce Clause power [of the U.S. Constitution] may be expansive, but it does not grant Congress the power to regulate noneconomic inactivity traditionally within the States' police power," the judge said.

Reiss said she doubts the legal fight will hinge on those cases. "I just think that smart litigators won't make that the battleground," she said. "That's not where I see the heart of the battle."

The arguments against Biden's vaccine mandate could take multiple forms, Reiss said, but "if they want to convince courts to strike these down, they're going to have to try and find a way to thread the needle" without undercutting existing workplace rules.

OSHA emergency power

She noted that such federal regulations have been legal for more than 50 years — since the creation of the Occupational Safety and Health Administration, or OSHA — and courts tend to be conservative about undoing them.

However, the OSHA case is unique because the agency invoked its little-used emergency authority. OSHA can fast-track rulemaking if the Labor secretary determines a safety standard is necessary to protect workers from a grave danger.

Prior to the pandemic, the agency had not issued an emergency standard since 1983. The courts have halted or overturned four of the 10 emergency standards issued by OSHA prior to the vaccination requirements. A fifth was partially vacated.

"Vaccination is the single best pathway out of this pandemic. And while I would have much preferred that requirements not become necessary, too many people remain unvaccinated for us to get out of this pandemic for good," Biden said in a statement on the mandate.