The 10th is pretty EXPLICT. All powers not delegated nor prohibited are reserved to the states.
I'd quote Chief Justice Chase again but that wouldn't make a difference to you would it? So let me try another tack. WhoIsJohnGalt has been around a lot lately, he's wacky enough to be admired by the southron contingent, and at one point a few says ago he posted a quote from a majority decision written by Justice Thomas, a man he apparently admires. That quote was:
"As far as the Federal Constitution is concerned... the States can exercise all powers that the Constitution does not withhold from them. The Federal Government and the States thus face different default rules: where the Constitution is silent about the exercise of a particular power - that is, where the Constitution does not speak either expressly or by necessary implication - the Federal Government lacks that power and the States enjoy it. These basic principles are enshrined in the Tenth Amendment, which declares that all powers neither delegated to the Federal Government nor prohibited to the States - are reserved to the States respectively, or to the people [of the States]." -- U.S. Term Limits v. Thornton, 1995
Implicit in the Constitution is the need for Congressional approval for any change in the status of a state, and the fact that states cannot act, or cannot act without congressional approval, where the interests of other states is involved. The southern acts of unilateral secession violated the Constitution. They were illegal.