Felix S. Cohen wrote:Legal concepts (for example, corporations or property rights) are supernatural entities which do not have a verifiable existence except to the eyes of faith. Rules of law, which refer to these legal concepts, are not descriptions of empirical social facts (such as the customs of men or the customs of judges) nor yet statements of moral ideals, but are rather theorems in an independent system. It follows that a legal argument cqan never be refuted by a moral principle nor yet by any empirical fact. Jurisprudence, then, as an autonomous system of legal concepts, rules, and arguments, must be independent both of ethics and of such positive sciences as economics or psychology. In effect, it is a special branch of the science of transcendental nonsense.
And here is a link to his wikipedia page, so as to help you begin a deeper study of this man:
http://en.wikipedia.org/wiki/Felix_S._Cohen
Having studied him you will be able to wax far more eloquent than merely to object "The law is an ass!"
Namaste