Complex sentence: It is illegal in all forms of baseball, and has different penalties depending on the situation: if there is no one on base, the pitch is called a ball, but if there are any number of runners on base, it is ruled a balk.
Split into simpler sentences: It is illegal in all forms of baseball, and has different penalties depending on the situation. If there is no one on base, the pitch is called a ball, but if there is any number of runners on base, it is ruled a balk.