Republican presidential hopeful Rick Santorum has called himself a "very strong supporter" of the 10th Amendment while simultaneously asserting that "the idea that the only things that the states are prevented from doing are only things specifically established in the Constitution is wrong." If elected president, Santorum also says he would put a stop to any state trying to legalize gay marriage:

I will get involved in that because the states, as a president I will get involved because the states don't have a right to undermine the basic fundamental values that hold this country together. America is an ideal. It's not just a constitution, it is an ideal. It's a set of morals and principles that were established in that declaration, and states don't have the right, just like they didn't have the right to do slavery.

Writing at the Volokh Conspiracy, Case Western Reserve law professor Jonathan Adler suggests that Santorum "might want to read" the 10th Amendment instead of just pretending to know what it says:

The Constitution only prohibits states from doing those things the Constitution prohibits, and the federal government may only constrain state autonomy pursuant to those powers delegated to the federal government. Santorum may think same-sex marriage is wrong, but nothing in the Constitution prevents states from recognizing same-sex marriage nor does anything in the Constitution authorize the federal government to stop states from doing so.

For more on Santorum's long crusade against limited constitutional government, read Jonathan Rauch on Santorum's "frothy mixture of collectivism and conservatism," and then check out Reason.tv's report from the Iowa caucus: "Rick Santorum on the Freedom to Impose Your Values."