王法 is rhetorical and old-fashioned - literally 'the king's law,' from imperial times. Modern formal law is
法律;
法令 for decrees.
王法 today survives mainly in indignant exclamations (
你心中还有没有王法 - 'have you no respect for the law?!'), period dramas, and wuxia. It carries moral weight that
法律 doesn't.