The enumeration in the Constitution, of certain rights, shall not be construed to deny or disparage others retained by the people.
When the newly drafted Constitution was first being debated, one of the biggest criticisms from the Antifederalists was that it lacked a bill of rights. The Federalists argued that a bill of rights was not only unnecessary, but that it might even be dangerous.
According to the Federalists, the new national government created by the United States Constitution was meant to be one of enumerated powers, unable to exercise any power that was not named in that document. A bill of rights, however, might be interpreted to imply that the national government could exercise any power that was not explicitly excluded. A bill of rights might also be interpreted as being a complete, exclusive list of individual rights, and might therefore have the perverse effect of limiting individual rights to those defined in the bill itself. But most Antifederalists were not persuaded by these concerns, and so the Constitution was ratified with a tacit understanding that Congress would propose a bill of rights without delay.
The 9th Amendment was meant to address both Federalist concerns about a bill of rights. First, it was designed to negate any suggestion that such a list implied that the national government possessed any additional, unenumerated powers. Second, the 9th Amendment was designed to clarify that the Bill of Rights is not exhaustive—it does not name every conceivable individual right. Other individual rights might very well exist. But this aspect of the 9th Amendment presents at least two additional questions. What are those other rights, if any? And who has the power to identify and define them?
Unfortunately, the modern Supreme Court has not really clarified the meaning of the 9th Amendment. While it has occasionally cited the 9th Amendment in cases discussing individual rights, it has tended to do so in tandem with other constitutional provisions, leaving the 9th Amendment’s specific effect unclear. Some individual justices have decried the use of the 9th Amendment to identify additional individual rights at all, especially when those rights are asserted against state governmental intrusion.