Important aspects of the federal government’s COVID-19 vaccination and testing requirements for larger private sector employers, including those in the promotional products industry, took effect on Monday, Jan. 10, but whether they’ll remain in play is uncertain as the U.S. Supreme Court considers the matter.

The mandate from President Joe Biden’s administration orders that workers at companies with 100 or more employees in the United States must be fully vaccinated against COVID-19 or submit to weekly coronavirus tests to confirm they don’t have the virus. The mandate affects more than 80 million private sector workers.

Starting Monday, businesses subject to the mandate were required to post their company’s vaccine policy, establish a database of workers’ vaccination status, allow workers paid leave to get the vaccine, and require unvaccinated employees to wear a mask on the job.

Promo products firms with 100 or more employees and other businesses in the same size category have until Feb. 9 to institute the weekly COVID testing of unvaccinated workers. After that date, the Occupational Safety and Health Administration (OSHA) will begin enforcement actions against businesses that are not complying with all aspects of Biden’s mandate.

“Employers need to take steps to immediately comply,” Domenique Camacho Moran, an employment attorney at New York-based law firm Farrell Fritz P.C., told The Hill.

Failure to comply could prove costly: OSHA is empowered to issue fines of up to $14,000 per violation. Furthermore, businesses that fail to adhere to the mandate could potentially be vulnerable to lawsuits if workers contract COVID while on the job.

Compliance could well prove difficult, though. Compiling an accurate record of employee vaccination status has been challenging for some firms, for instance. Perhaps even a bigger issue is the fact that demand for COVID-19 tests is at a fever pitch. Companies will be competing to get the requisite number of tests to check each unvaccinated employee every week for COVID.

Still, there’s the possibility the mandate could soon be moot. The Supreme Court is currently considering whether to affirm the mandate’s validity or to rule that it can’t legally be applied. On Friday, Jan. 7, the court heard arguments from federal attorneys in support of the mandate and lawyers for states/business groups that are seeking to have the requirements thrown out.

While the court’s liberal justices showed support for the mandate, conservative judges appeared skeptical that the White House has the legal authority to impose the requirements on businesses with 100 or more employees. The court is 6-3 majority conservative.

As NPR reported, Chief Justice John Roberts appeared to make his doubts about the regulation known when he said, “This is something the federal government has never done before.”

Conservative justices Neil Gorsuch, Brett Kavanaugh, Clarence Thomas and Samuel Alito “indicated even more strongly that, in their view, the regulation went too far,” NPR reported. “They argued that at minimum Congress would have to enact a new statute that specifically authorizes the vaccine-or-test regulation. The chief justice and Justice Amy Coney Barrett appeared less categorical in their approach, but both were clearly skeptical of the regulation.”

The Supreme Court’s three liberal justices indicated that they believe that the mandate is necessary as the nation continues to grapple with the COVID-19 pandemic, which is currently in another surge due to the omicron variant.

“This is a pandemic in which nearly a million people have died,” Justice Elena Kagan stated. “It is by far the greatest public health danger that this country has faced in the last century. We know that the best way to prevent spread is for people to get vaccinated.”

Justice Stephen G. Breyer said he would find it “unbelievable that it could be in the public interest to suddenly stop these vaccinations.”

Should the Supreme Court rule the mandate is not legal, thereby meaning it can’t be enforced, it’s likely “there will be many states, probably New York, California and other states, that decide it’s within their power to order this type of thing and we will have a fresh round of litigation over it,” civil rights attorney Harmeet Dhillon, told Fox News.