If the States did things that were unconstitutional then the FedGov can always reign them in. There is a huge difference between FedGov that acts as a simple check on the States to keep them within the confines of Constitutional Law, and a FedGov that feels the need to centrally manage and control.

For who could be free when every other man's humour might domineer over him? - John Locke (2nd Treatise, sect 57)