Jacob Sullum talks about the great expansion of federal hate crime that Congress is considering. This bill makes federal crimes out of most crimes, enabling double jeopardy.  The problem is that, under our federal system, the federal and state governments are considered separate sovereigns, and so while double jeopardy is generally prohibited, because each sovereign is considered to have its own, separate interest in prosecuting crime.
It’s a nice idea in theory, and it might even work out if Congress were truly limited to its enumerated powers. But Congress’ power over interstate commerce are now without limit. With this new hate crime law, a person could easily be acquitted by a jury in state court, and then brought to trial in federal court for the same act, under this “hate crime” law. The nexus to interstate commerce? Well, he used a gun see. And that gun once traveled over state lines. Lopez was supposed to deal with this problem, but who knows if that’s even still valid precedent, even if it might technically still be.