This article discusses federalism and deferent theories related to it. Federalism as a theory, as a concept and as an organizational structure refers to the distribution of powers between the two levels of the government. It stands for unity, cooperation, and interdependence between the central government and the component units. Being dynamic in nature, it adopts changes according to the prevailing conditions of the country. An attempt has been made to elucidate federalism from two broad perspectives of the classical approach and Modern approach. The classical approach restricts federalism to cooperation and independence with quasi federalism, coupled with the element of encroachment from the federal government. This approach is merely based upon the doctrine of legal formalism or formalism fallacy. The modern approach focuses on two cardinal principles of cooperation and interdependence. The modern theory is a broad term and encompasses many forms of federalism within its ambit.

This paper critically examines the 18th constitutional amendment of Pakistan, which is a revolutionary legal change and helped to see a huge adjustment of a federal form of government to provincial autonomy. The 18th Amendment provided for the abolition of the Concurrent Legislative List, the devolution of significant ministries, and reinforcement of intergovernmental institutions like the Council of Common Interests and the National Finance Commission. Although the amendment revitalized the federal spirit of the 1973 Constitution and gave the provinces the strength in legislative and fiscal areas, its early practice revealed the shortcomings in institutions and capacities. The paper concludes that sustainable federalism in Pakistan entails an enhanced level of intergovernmental coordination, institutional changes, and political commitment to handle the asymmetries between provinces.