It covers rights not explicitly stated by the Constitution or Bill of Rights. Obviously you know this, of course.
Obviously.
Try this on for size. I reserve the right make meth and sell it. The right to do so is not specifically enumerated, but the 9th Amendment says that rights retained by the people shall not be denied or disparaged. I have paid sales tax on all products that I have used to make it, so therefore I should be able to do whatever I want with it. Yet, it is illegal to make it and sell it, or even to purchase large quantities of the materials used to make it. There is a law that was voted on by Congress. By your logic the law in question would be unconstitutional. But it isn't.
My point is that just because the Constitutional doesn't specifically allow something, it doesn't mean that it cannot be done. The 9th amendment applies to Congress as wee, you know, as they are made of people, representing people.