The U.S. Supreme Court heard arguments Friday in a high-stakes public session to decide whether the U.S. government can begin enforcing sweeping COVID-19 vaccine requirements affecting nearly 100 million workers.

For three hours and 40 minutes, the justices heard oral arguments over federal vaccine and testing rules for businesses with 100 employees or more, and on vaccine mandates for health care workers at facilities receiving Medicaid and Medicare funding.

Enforcement of the policies, which were announced in November, has been put on hold pending resolution in the high court.