There is an 'ethical conduct in business dealings and contracts' clause that is vaguely worded and which is what they might try to get him with, the argument being that Sterling's comments were unethical and caused damage to the labor relationship between the NBA and the players. If the NBA pulls the trigger on that then it'll be the legal catfight to end all legal catfights. A media whore like Sterling would love it. And I suspect the NBA has no other choice than to try. Certain people will demand it.
At the end of the day I suspect that the NBA will have to be happy with the punishment they have given him. Sterling can be a sports mogul in name only. While the NBA cannot force him to sell they likely can appoint people to manage the team since Sterling can no longer hire or fire. Eventually Sterling will die and his heirs will get it.
I wonder if the NBA goons will help him along to his “final reward”.