Roberts' opinion for a unanimous Court upheld a regulation issued by the Treasury Department that categorically excluded those working at least 40 hours a week from eligibility for a student worker exemption from Social Security taxes. The regulation was challenged by the Mayo Foundation, which employed medical residents as part of their continuing hands-on education. The Court clarified that Chevron deference applied to the Treasury Department's regulation, notwithstanding prior decisions to the contrary that had applied a less deferential standard to tax regulations. Applying Chevron, the Court found that the statutory exemption was silent on the definition of "student" and its specific application to medical residents, which left the issue to the Treasury Department as the implementing agency, and that the full-time student regulation was a reasonable construction of the statute .
Roberts denied an application for a stay. The petitioner sought certiorari of his state court conviction. The stay he sought, however, was not of the state court judgment, but of the briefing schedule entered by the district court in which he had separately initiated habeas proceedings. Roberts ruled that the petitioner had not established that he was entitled to that relief.