The enumeration in the Constitution, of certain rights, shall not be construed to deny or disparage others retained by the people.
In real plain language, the authors, and by extension the states, legislatures and people who adopted this constitution, said that the Constitution limits the government to those activities defined therein. That they failed to prohibit something in The Bill of Rights does NOT make it okay to steal later.
One of the complaints levied against the Bill of Rights during ratification arguments was that someone might someday claim that rights not spelled out were not valid. After all, why did they spell out the ones they did? So this amandment clarifies their intentions.
They didn’t have an inkling that the primary means of communicating would be the Internet. They couldn’t have enumerated our right to be secure in our electronic papers. They simply didn’t have the language to describe it.
But we have that right.
Most specifically, NOTHING in the Constitution grants the federal government or any government to snoop on our correspondence. In case someone attempts to go BEYOND the Constitution to do that, this 9th Amendment is supposed to serve as a reminder, that THE PEOPLE retain their right to privacy regardless of its absence in the rest of the Bill of Rights.
And so on….