"The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved for the States respectively, or to the people."

If we take "United States" to be synonymous with the federal government, which I think is reasonable, then the amendment means that whatever powers the government doesn't have, either the states themselves or the people have.

I think that it basically means that since the Constitution is really more a whole bunch of "thou shalt nots" as opposed to "thou shalts," practically speaking, the federal government has no power except to protect the rights of its citizens.

It does also establish, however, that the responsibility of the federal government to protect the rights of the people does supercede the rights of the states. If you really think about it, I mean. This means that state laws have to adhere to the Constitution. In fact, the only real purpose of the federal government is to make sure they do.

That's the way I interpret it, anyway.