Ball hits a tree

[Manny A]

Originally Posted by BretMan

(NCAA)

1.27 Ground Rule
An allowable amendment of the playing rules to accommodate a particular
circumstance (usually a field condition). Ground rules cannot conflict with or
supersede a playing rule.

And the way I read that is that you cannot create a ground rule when a book rule already exists to address the situation.

For example, there's a gate behind first base with a gap underneath, and a thrown ball can go through it. That's clearly something covered by the rule on balls going through or under a fence. So you cannot create a ground rule for it, especially one with, say, only a one-base award.