The Ninth Amendment states, The enumeration in the Constitution, of certain rights, shall not be construed to deny or disparage others retained by the people.” It was designed to work with the Tenth Amendment to reinforce limits on the federal government.
The original Constitution contained three types of restrictions on federal power:
Type 1: The Constitution listed things the government could not do (e.g., pass an ex post facto law).
Type 2: The Constitution enumerated the powers the government was to have (e.g., regulate interstate commerce, but not agriculture).
Type 3: The Constitution included specific restrictions on specific powers (e.g., Congress could appropriate money for an army, but only for a two-year period).
Some argued that Type 1 should be expanded with a Bill of Rights. But others (James Madison among them) pointed to a risk in that proposal. Because of the legal maxim Designatio unius est exclusio alterius (the designation of one thing implies the exclusion of another), adding a Bill of Rights might encourage people to disregard the Type 2 and 3 restrictions on federal power.
When the demand for a Bill of Rights prevailed, Madison agreed to draft one – but he included what became the Ninth Amendment to make it clear that expanding Type 1 did not mean abandoning Types 2 or 3.
A key to reading the Ninth (and Tenth) Amendments properly is to know that the Founding Generation often used the words “right” and “power” interchangeably. (We more rarely do the same, as when we refer to the President’s “right” to veto a bill.) That is how they were used here. If you sometimes read the word “rights” in the Ninth Amendment as “powers” and “powers in the Tenth Amendment as “rights,” you can better understand their meaning.
Few parts of the Constitution have been so misunderstood as the Ninth Amendment. For example, some have argued that it reserved a mass of “natural rights” that the Courts should enforce against the federal, and even the state, governments – such as abortion, property, and contract rights. That misunderstanding arises from failure to understand that “rights” in the Ninth Amendment means “powers.”
The Ninth Amendment was not designed to enable the Courts to create new rights – or even to recognize old ones. It was designed to work with the Tenth Amendment to preserve the Constitution’s other restrictions on federal power.