Lio Rush made his AEW debut at Double or Nothing as the final entrant in the Casino Battle Royale.
AEW President Tony Khan talked about this during the post-Double or Nothing media scrum. This is where he said he has a handshake deal with Rush.
Dave Melzter revealed in the latest edition of Wrestling Observer Radio that Rush has actually signed a contract with NJPW recently. Thus, NJPW allowed him to make the AEW appearance and Rush may work more shows with AEW but likely won’t be signed to the company.