In NFIB v. OSHA, the US Supreme Court granted the application to stay the OSHA rule requiring that employers with at least 100 employees require covered workers to receive a COVID–19 vaccine or else wear a mask and be subject to weekly testing. Using the contested major question doctrine, the Supreme Court held that the challenged rule went well beyond the OSHA power to set workplace safety standard and was effectively a broad public health measure not expressly allowed by the Congress. The per curiam opinion as well as the concurring and the dissenting opinions provide significant guidance related to the principles of the separation of powers and of democratic legitimacy within the administrative state.