The University is not compulsory but it is the rules that you must follow.This means that if you want to study at University, that is, you must respect the rules of the University.
University is not compulsory, but it is the law that you have to follow , which means if you want to enroll at the university that is, you have to respect the rules set by the University.
University compulsory but it is, as a rule, you must follow the , which means that if you want to enter the University, that is, you have to respect the rules of location.