Natural law is the foundation upon which the spirit of the Constitution is built. Many of the ideas and terms of art used in the Constitution cannot truly be understood without a deep understanding of the natural law philosophy the Founders held. It wasn’t until the “New Deal” era in the early 20th century that many lawyers and politicians abandoned these ideas.

In many ways, the common law and the natural law are entwined, but they are not the same. The common law was explained by judges over many generations creating a well-known “common” set of rules. The judges of that era intended to use the natural law to determine what those common law rules were. The common law is explained by judges, but the natural law is the nature of people rather than whatever any judge says.

A core part of the natural law are “natural rights.” Natural rights do not comprise all of the natural law, but perhaps they are the most important part. Natural rights specify what acts one person cannot morally do to another. They do not specify what a person should do. The invocation in the Declaration of Independence of the right to “life, liberty and the pursuant of happiness” is one way of expressing these natural rights. Another is the rights of “life, liberty and property” in the Fifth Amendment.

These natural rights are rights which everyone has (“all men are created equal”) and do not overlap with other people’s rights. No person has a right to harm another as that means one person’s right interferes with another person’s right. That would not be equal. Nor do they guarantee any specific instance of property or service; rather, they guarantee the right to purchase property or services. If two people had the right to the same piece of property, then their rights would interfere with each other, and that never occurs in natural rights. Likewise, a right to a specific service would interfere with the provider of that service’s control over their own work.

While we can speak of natural rights at a high level of generality, like the right to liberty, there are derivative rights that are included within that. The right to freedom of speech, for instance, is a subset of the broader right to liberty. The right to choose when to go to bed or what clothes to wear are all rights within the broader right to liberty. This is true for the other natural rights as well. For instance, the right to property includes the subset rights to possession, sell, subdivide, lease, mortgage, to exclude others, among others.

It is with this understanding that we can start to see what the Ninth Amendment was designed to do. The Founders knew that there were an infinite number of subset rights within the broader right to liberty and many of the other natural rights. The right to freedom of speech is one of them, but so is the right to jump up and down or to sing a song. It would have been impossible to list all of a person’s natural rights, the best we can do is speak in broad generalities like the right to “liberty” in the Fifth Amendment.

The Ninth Amendment recognizes that there are rights “retained by the people.” The Ninth Amendment doesn’t create these rights, they are natural rights which pre-exist government. But the Founders wanted to provide explicit protections for at least some of these natural rights (like the freedom of speech), out of extra caution that a tyrannical government could improperly ignore these very important natural rights.

The Ninth Amendment says that enumerating certain rights in the Constitution, like the right to freedom of speech, does not mean the other natural rights are not just as protected as they were before  freedom of speech was specifically spelled out. Not only can the existence of these other rights not be “denied” because they were not specifically mentioned; they cannot even be disparaged. The prohibition on disparaging these rights means they cannot be given a lower level of protection just because they were not specifically mentioned. Judges cannot, for instance, strongly protect the freedom of speech because it is mentioned in the Bill of Rights, but give very weak protection to the right to sing because it wasn’t mentioned.

That doesn’t mean that everything someone could call a “right” is protected by the Ninth Amendment. Only those rights “retained by the people” which referred to the natural rights were recognized as protected rights.

These ideas around natural law and natural rights are critically important to properly understanding the meaning of the Constitution and especially the Bill of Rights.