Mark Lemley, a Stanford Law professor and expert in trademark law, told Ars that X might be able to defend the Twitter marks if it can show that it is still using them.

“Mere ‘token use’ won’t be enough to reserve the mark,” Lemley wrote in an email. “Or [X] could defend if it can show that it plans to go back to using Twitter. Consumers obviously still know the brand name. It seems weird to think someone else could grab the name when consumers still associate it with the ex-social media site of that name. But that’s what the law says.”