Though there are no specific laws prohibiting cow tipping, however there are several laws related to cow tipping such as trespassing, animal abuse, property damage, and in some states... livestock damage, which carries a heavier sentence b/c cows are the own's livelihood and damaging this constitutes not only the cost of the cow, but his business.
Cow tipping is extremely harmful to the cow as they are huge animals that are not accustomed to being tipped over while they slept. At simplest, they may break a leg, but often they suffer brain damage and become useless, eventually need to be put down.