Heinrich A. Rommen in The Natural Law: A Study in Legal and Social History and Philosophy, describes Natural Law by using the great Hugo Grotius’ definition: The law of nature [ius naturale] is a dictate of right reason which points out that an act, according as it is or is not in conformity with rational [and social] nature, has in it a quality of moral baseness or moral necessity; and that, in consequence, such an act is either forbidden or enjoined by the author of nature, God.
Russell Kirk in Roots Of American Order describes the pagan Cicero’s Stoic-influenced theory of law:
Human laws are only copies of eternal laws. Those eternal laws are peculiar to man, for only man, on earth, is a rational being. The test of validity for the state’s laws is their conformity to reason. This reason, when firmly fixed and fully developed in the human mind, is Law. And so they believe that Law is intelligence, whose natural function it is to command right conduct and forbid wrongdoing. Thus, natural law forms the basis in creation for our intuitions of right and wrong, and is the context for our ability to reason.
Cicero himself discusses the universal existance of natural law across the world:
True law is right reason in agreement with Nature…it is of universal application, unchanging and everlasting… we need not look outside ourselves for an expounder or interpreter of it. And there will not be different laws at Rome and at Athens, or different laws now and in the future, but one eternal and unchangeable law will be valid for all nations and for all times, and there will be one master and one ruler, that is, God, over us all, for He is the author of this law, its promulgator, and its enforcing judge. Whoever is disobedient is fleeing from himself and denying his human nature, and by reason of this very fact he will suffer the worst penalties, even if he escapes what is commonly considered punishment.
A number of famed legal expositers have stated explicitely that a bad law is not binding. Consider Thomas Aquinas, considered history’s greatest authority on natural law, on just and unjust laws:
Laws framed by man are either just or unjust. If they be just, they have the power of binding in conscience, from the eternal law whence they are derived, according to Prov. 8:15: “By Me kings reign, and lawgivers decree just things.” On the other hand laws may be unjust in two ways: first, by being contrary to human good… The like are acts of violence rather than laws; because, as Augustine says (De Lib. Arb. i, 5), “a law that is not just, seems to be no law at all.” Secondly, laws may be unjust through being opposed to the Divine good: such are the laws of tyrants inducing to idolatry, or to anything else contrary to the Divine law: and laws of this kind must nowise be observed, because, as stated in Acts 5:29, “we ought to obey God rather than man.”
Probably no American is more celebrated for his views of law, tyranny and the right to engage in civil dissobedience than Dr. Martin Luther King, Jr. In his “Letter from a Birmingham Jail” Martin Luther King, Jr. said,
You express a great deal of anxiety over our willingness to break laws. This is certainly a legitimate concern. One may well ask: “How can you advocate breaking some laws and obeying others?” The answer lies in the fact that there are two types of laws: just and unjust. I would be the first to advocate obeying just laws. One has not only a legal but a moral responsibility to obey just laws. Conversely, one has a moral responsibility to disobey unjust laws. I would agree with St. Augustine that “an unjust law is no law at all.” Now, what is the difference between the two?
How does one determine whether a law is just or unjust? A just law is a man made code that squares with the moral law or the law of God. An unjust law is a code that is out of harmony with the moral law. To put it in the terms of St. Thomas Aquinas: An unjust law is a human law that is not rooted in eternal law and natural law. Any law that uplifts human personality is just. Any law that degrades human personality is unjust. There is nothing new about civil disobedience. It was evidenced sublimely in the refusal of Shadrach, Meshach and Abednego to obey the laws of Nebuchadnezzar, on the ground that a higher moral law was at stake.
It was practiced superbly by the early Christians, who were willing to face hungry lions and the excruciating pain of chopping blocks rather than submit to certain unjust laws of the Roman Empire. To a degree, academic freedom is a reality today because Socrates practiced civil disobedience. In our own nation, the Boston Tea Party represented a massive act of civil disobedience.
John Locke, the Founders’ model for much American legal and government theory says the following about unjust government: “Whenever the power that is put in any hands for the government of the people, and the protection of our properties, is applied to other ends, and made use of to impoverish, harass or subdue them to the arbitrary and irregular commands of those that have it; there it presently becomes tyranny, whether those that thus use it are one or many”. (Second Treatise, Chapter 18).