American constitutionalism today has long outgrown the model that worked so well for the Young Republic. The original federal system that allocated power between the state and national governments has been transformed into what can now realistically be described as a unitary national state. A good deal of this has been less a product of design than of necessity as the nation adjusted to problems that had to be addressed at the national level. Problems relating to monopoly and the concentration of economic power, drugs, illegal immigration, and international terrorism are beyond the reach of the states. They did not exist in the early Republic but today are everyday concerns in the life of the nation. The upshot has been a steady and growing concentration of power at the center that over the years has gradually turned state sovereignty into essentially a political fi ction.