Federal vs. Unitary Design
How constitutions distribute power between central and sub-national governments — federation, devolution, and the spectrum between centralization and autonomy.
The Centralization Spectrum
Every state must decide how to distribute power between the central government and sub-national units (states, provinces, regions, cantons). At one extreme, a unitary state concentrates all constitutional authority at the center — local governments exist only because the central government creates and empowers them. France, Japan, and most Scandinavian countries follow this model. At the other extreme, a federation constitutionally divides sovereignty between the central government and sub-national units, each with its own protected sphere of authority. The US, Germany, India, Brazil, and Australia are federations.
In practice, the spectrum is continuous rather than binary. The UK is formally unitary but has devolved significant powers to Scotland, Wales, and Northern Ireland. Spain is formally unitary but its 'autonomous communities' have more self-governance than some federation members.