When is the last time a trade got voided by the commish? In all seriousness, people pay hundreds of millions of dollars to own these teams. They should have the right to do with them what they will. If the league has a problem beyond the traded players (such as Florida taking advantage of taxpayer dollars for the stadium) then they can move forward with trying to remove the owner/force to sell.
Owners answer to the fans. If the fans do not like a move, they will not show up. But its a real pandora's box to start veto'ing trades because one side won. Such a bad idea.
The ONLY time a trade should be veto'd is if 2 owners were colluding/conspiring together.