Right, but the idea is EVERYONE draws from the same set of balls so no one team can benefit from altering the balls. The NY Yankees don’t keep their own baseballs for use only when it’s their turn to pitch. Seems like that kind of rule begs for stuff like this to happen.
Sure they can. How do you think the umps get the balls? Someone from the home team has to hand them over. The ump doesn’t select them. They’re all new so it really doesn’t matter as much. Regardless, baseball has a different rules regarding balls, ie. they tend to replace one every time it hits the ground.
But there was a stink a few years ago about the Rockies making theirs more humid.
http://www.popsci.com/entertainment-amp-gaming/article/2008-11/why-do-colorado-rockies-keep-their-baseballs-humidor
Ball manipulation has a long tradition:
http://a.espncdn.com/mlb/columns/neyer_rob/1380568.html