It needs a gut for a mother to stand by the law rather than protecting her own son. If a mother is capable of showing such character, unlikely her son would turn out to be a rule breaker.
However, in this instance, if the son is a deliberate defaulter then, I guess, he should not be protected. If the mother wants to stop her son from doing any such act in future, she has to be strict in the first place itself. This is not about being true to the law, it is about taking a corrective measure. If a mistake is entertained today, it might lead to bigger crimes tomorrow. Being a mother, it is her responsibility to channelize her son to the right direction. And, every journey starts with a single step.