Catholicism and Natural Moral Law
A pillar of the Catholic set of laws is its understanding of natural moral law, which addresses laws that aren’t written but nevertheless known by all men and women who have the use of reason. It uses basic common sense, prudence, and justice.
Moral law is natural because it’s known by reason — not written in stone or on paper, like the Commandments or the Bible. It’s moral because it applies only to moral acts — actions of human beings that involve a free act of the will. (It doesn’t apply to animals, because they don’t have the use of reason.):
Under natural moral law, Cain sinned when he murdered his brother Abel even though he committed the crime long before Moses received the written laws of the Ten Commandments. Because of the natural moral law, Cain knew it was wrong to commit murder before the Fifth Commandment ever came along.
Because of the natural moral law, trials for war crimes can be conducted against anyone who commits genocide or mass murder regardless of the person’s religion or lack of it. A Nazi couldn’t have used the defense that he didn’t recognize the authority of the Bible, because even the most evil of Nazis still had the use of reason, and reason is what discovers the natural moral law for each and every man and woman.
Just obeying orders or following the civil law won’t cut it either. An immoral act violates the natural moral law even if it conforms to the local civil law:
Slavery was immoral and contrary to natural moral law even though the U.S. Supreme Court (1857) upheld it until it was overturned by the 14th Amendment (1868) after the Civil War.
The Nuremburg Laws of Nazi Germany (1935) also violated the natural moral law, because they deprived Jews of their citizenship and paved the way for confiscation of personal property, deportation, incarceration, and doomed many to the concentration camps.
The legalized racial segregation in South Africa from 1948 to 1991, known as apartheid, defied the natural moral law.
In all these cases, the civil law endorsed, tolerated, or promoted horrible injustices, precisely because the natural moral law was being violated. A government, a constitution, a law, or an amendment doesn’t grant personhood. It comes from human nature made in the image and likeness of God. Jew and Christian, born and unborn; the natural moral law exists despite what political parties and civil authorities legislate to the contrary.