Federal Powers and the Principle of Subsidiarity.

Federal systems across the world are generally designed according to the principle of subsidiarity, which in one form or another holds that the central government should play only a supporting role in governance, acting if and only if the constituent units of government are incapable of acting on their own. The word itself is related to the idea of assistance, as in “subsidy,” and is derived from the Latin “subsidium,” which referred to auxiliary troops in the Roman military. See Oxford Latin Dictionary s.v. (1983)