The Maloofs are the key.
Hansen's supporters keep mentioning tortious interference with contract etc. etc., but entirely apart from whether that would be a wise suit to bring, whether its even possible or not depends on contract law, and specifically what the NBA's laws say both about when a sale becomes official, and restrictions on parties bidding for a team. They want to claim that Hansen contract is a done deal and the NBA is breaking it. Depending on how the NBA's rules are written however, it may never have been a done deal until the NBA signed it as well. In addition, there are restrictions on bidding parties being allowed to sue the league, but I don't know what they are.
The potential monster in the closet of course is antitrust, but the Maloofs are the ones much better positioned to go down that dark road than Hansen. Make no doubt about it, they are the danger. Hansen has found a set of soulless stooges to potentially do his dirty work for him and is trying to bribe them to try the same sort of league busting tactics people like Al Davis have tried in the past. He is trying to give them the ability to claim the NBA is cheating them of $100mil. Or more realistically, he is trying to threaten the league with that so that the league will cave to his wishes.