A federal appeals court in New Orleans on Monday became the latest to hear arguments on whether President Joe Biden overstepped his authority with an order that federal contractors require that their employees be vaccinated against COVID-19.

The contractor mandate has a complicated legal history. It is being challenged in more than a dozen federal court districts, and the mandate has been blocked or partially blocked in 25 states. At one time, enforcement was blocked nationwide under a ruling by a Georgia-based federal judge. But an appeals court in Atlanta narrowed the scope of that ruling to the seven states that had sued in that case.