Lott and Federalism: James Ostrowski on lewrockwell.com:

What do we do about abuses of federal power? Create a world government? I hear silence. So let’s sum up. Liberals say that when state governments abuse their power, we transfer that authority to the federal government. However, when the federal government abuses its powers, they refuse to follow the same logic and strip their beloved federal government of its powers.

Of course, some people would be happy with a world government. But the same problem applies: what happens when the world government gets something wrong? What if it decides, for instance, to adopt the War on Drugs as a global policy? What if it decides to dispossess everyone who is "rich", which would include all Americans? What if it it decides that women should not work outside the home?