This article is the best I've found on the legal aspects:
http://sportsillustrated.cnn.com/nba...ban/index.html
Sounds like the ethics clause that will likely be the angle used to justify the expulsion centers around behaviors that cause economic damage to the NBA. Certainly the case here, but could also apply equally if an owner came out and said he hated America, etc. (or something else equally likely to stir up much public consternation). That's where things seem to certainly be 'slippery' and wouldn't be surprised to see the owners push for a morals clause to define these behaviors and protect themselves going forward.
Regardless, the ethics clause is somewhat ambiguous. Sounds like a protracted lawsuit can likely be expected?