In the unlikely event that a disclaimer like that was actually enforced, there would need to be extensive record-keeping by the team. If the receipt for say a GU bat said "PLAYER NAME Game Used Cracked Bat," they would also need photos of the bat to prove you were selling that specific gamer. You could easily say "Well, the player used 50 bats that year!"

I'm also not sure they even have the ability to say that. If you buy an item, it is yours.