This is ridiculous. Stack is included to make the salaries work, and NJ is going to buy him out because they don't want his salary. Where he goes after that is not something that interests Jersey, he's getting bought out regardless. All Stack is done is say that when that happens, his preference is to return to Dallas, and he probably doesn't need to read tea leaves to figure out the Mavs would like to have him back. Anything can happen in 30 days - a Western compe or can make a $$ offer the Mavs can't match, the Mavs might not be done making deals to improve their roster and won't have the salary slot or roster spot to sign Stack.
It was fine to stick to the rules when Amare and Boris broke them, and Stern swore up and down his hands were tied, and it would set a horrible precedent if he tore up a rule on the fly because it was inconvienent. Now he's going to do just that. Apparently his hands aren't tied after all. The worst you can say about this is that Stack's preference to go back to Dallas violates the spirit of the 30-day rule but not the letter. If they find this distasteful so much, they can change the rule in the offseason.
And for the record, I don't like the trade, and only grudgingly want it to go through for team chemistry reasons. This is bull .