I don't know that any of the major professional sports have made any noise about attempting to seat a partially full stadium. If the had though, I'm sure state Health Departments would have some jurisdiction over it. We've already seen that play out in MLB with the Toronto Blue Jays and their "home" stadium saga, and with the Nats where the DC Health Dept. wouldn't clear Juan Soto until he completed their required quarantine period after a (likely false) positive test.

They have far more to lose from TV contracts if they have to cancel the games, than they have to gain from selling a few tickets. Not worth the risk.