In her dissenting opinion in Gonzales v. Raich, Justice O'Connor wrote:
We enforce the outer limits of Congress Commerce Clause authority not for their own sake, but to protect historic spheres of state sovereignty from excessive federal encroachment and thereby to maintain the distribution of power fundamental to our federalist system of government.
James Madison would have disagreed:
In the compound republic of America, the power surrendered by the people is first divided between two distinct governments, and then the portion allotted to each subdivided among the distinct and separate departments. Hence a double security arises to the rights of the people. The different governments will control each other, at the same time that each will be controlled by itself.
The Federalist No. 51, p. 323 (C. Rossiter ed. 1961) (J. Madison). By limiting the states and Congress to their proper prerogatives, the People would enjoy greater freedom since the structure of federalism would prevent Congressional overreaching into local affairs. The people would have two servants, not two masters. Federalism is concerned with individual liberty, not "state sovereignty" or "power."