It is often cause of much debate to determine which powers rest with states and which ones with the federal government. At times, there can even be contradictory laws on state and federal levels as you saw in today's extra material.
The 10th amendment says the states have the power to determine these things unless the Constitution specifically grants such power to the federal government, but the Supremacy clause and the Necessary and Proper clauses strengthen the authority of the federal government.
Is there necessarily a problem with contradictory, unreconciled laws? And if so, how are we to settle these disputes? Also, do you think states rights are more commonly evoked by conservatives or by liberals?