The Nets are fined $50,000 for letting Kyrie Irving into their locker room.

The N.B.A. fined the Brooklyn Nets $50,000 for allowing guard Kyrie Irving to enter the team’s home locker room during Sunday’s game against the Knicks. Mr. Irving has not been vaccinated against Covid-19 and thus was not allowed to be with the team at Barclays Center.

Mr. Irving had attended the game as a spectator, with a seat in the front row.

Under New York City law, Mr. Irving cannot play in games at Barclays Center because of a vaccine mandate for New York City-based workers who perform in-person work.

While Mayor Eric Adams loosened some vaccine requirements earlier this month, he has left in place the private-sector mandate. Under the N.B.A.’s health and safety protocols, teams must follow local decrees.

The Nets declined to comment.

During a public appearance on Sunday, Mr. Adams responded to a heckler who urged him to let Mr. Irving play: “Listen, you’re right. Kyrie can play tomorrow: Get vaccinated.”

The Nets forward Kevin Durant called the rule “ridiculous” after the game against the Knicks. He also criticized the mayor.

“It just feels like, at this point now, somebody is trying to make a statement or point to flex their authority,” Mr. Durant told reporters. “Everybody out here is looking for attention. That’s what I feel like the mayor wants right now: some attention.”

Minutes after the N.B.A. announced the Nets’ fine on Monday, Mr. Durant issued a statement through the Nets and softened his stance toward Mr. Adams.

“The last two years have been a difficult and painful time for New Yorkers, as well as a very confusing time with the changing landscape of the rules and mandates,” the statement read. “I do appreciate the task the mayor has in front of him with all the city has been through. My frustration with the situation doesn’t change the fact that I will always be committed to helping the communities and cities I live in and play in.”

Mr. Irving’s vaccination status has vexed the Nets for the entire season. He has played in only 18 of the team’s 68 games, in part because the mandate has barred him from playing home games, and he has refused to get vaccinated. Mr. Irving is allowed to play in road games where cities do not have vaccine mandates. Only Toronto, where the Raptors play, prohibits unvaccinated visiting players from competing.