What is federalism? The answer is that federalism, in my view, is another form of the separation of powers. But whereas the separation of powers separates legislative, executive and judicial power at the national level, what federalism does is it separates power between the national government in the United States the state governments in the United States. And it is the case that it was the state governments, or at least popular conventions in nine of the 13 states that created the federal Constitution and therefore the federal government, but the federal government under the US Constitution is a government of limited and enumerated legislative powers. And there are significant powers that are still retained by the states. The state governments in the United States are what are called “governments of general jurisdiction.” That is to say they have what Professor Richard Epstein sometimes calls the police power, the power to protect the public health, safety and welfare. State governments can regulate people's activities in ways that the federal government lacks the enumerated power to do. I think the argument for federalism and part of the definition of federalism is that it comes back to the famous quote from Lord Acton that power corrupts and absolute power corrupts absolutely. It's good to have bicameralism in the legislative branch, but it's even better to combine the benefits of separation of powers and bicameralism with a further division of power between the national government and the state governments. And in the United States, happily, we have that degree of protection.