Amendment X
The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people.
The modern "Liberal" has long tried to ignore the existence of this sentence. This is where abortion, socialized medicine, welfare, and a few other hot button issues should actually reside. They ignore it because they know their power lies in Congress, not in the individual states. "Liberalism" is strongest in the most populated areas, the most populated areas are few and far between, but they hold the most power in Congress.
It is interesting that they use it when they want it though. Oregon used it just two years ago when they took the Bush Admin to court, the Supreme Court, for the right to use Federally Illegal drugs to prescribe for suicide. I disagree with the suicide law, but I agree with the Supreme Court in their ruling in favor of Oregon.