Kevin Nash, and presumably other ex-WCW talent under some form of WWE contract, have been banned by WWE from attending Revolution in any capacity for Sting’s last match
It's pretty funny because they (WWE) have no issue when it's the other way around i.e. Punk showing up backstage at Raw last year and the Britt Baker sighting at an NXT PLE. Tho at the same time it's not surprising considering that WWE banned Kevin Smith and his boy and tried to ban Snoop for appearing on an AEW show.