Most no-trade lists correlate pretty well with tax rates, when you look at it. Teams need permission to trade somebody to the Dodgers or Giants, but Mariners, Rays, Rangers are fair game.
Related, a lot of unique deals are jock tax dodges. Liam Hendriks's current deal, for example. You can do things with signing bonuses and spreading them out or allowing them to be taxed in a home state instead of the state the games are played.