Three ways of sharing government powers
In constitutional systems, powers of a central government may be shared with smaller governments within the boundaries of the central government in one of three different ways:
In a unitary system, the central government has all major powers. Smaller governments within the boundaries of the central government, which could be called states, provinces, prefectures, or counties, have very little power. In those systems, power is delegated from a central government to subgovernments within the central government's boundaries; yet the grant of power may be rescinded at the will of the central government. The relationship between state governments and local governments, such as county governments, cities, and school districts, in the United States is that of a unitary system. Many nations have unitary systems, especially those that do not occupy large territories. Examples of such nations are the United Kingdom, France, Japan, the Netherlands, and China, the last-mentioned being the exceptional case of a large nation that has a unitary system.
In a confederal system, the smaller governments within a larger political unit have the major power, and the central government has very limited powers. Switzerland has had such a system of government, where cantons held major power and the Swiss government had relatively little power. The political systems of the Articles of Confederation and the Confederate States of America are also examples of confederal systems.
In a federal system, power is divided and shared between the central government and the smaller governments within the same territory. This is the system of government created by the framers of the United States Constitution. In such a system, the national government has very important powers, state governments have very important powers, and in some cases powers are shared between the two systems of government. Modern nations that have federal systems include Canada, Germany, Belgium, Australia, and Brazil.
Powers granted to the federal government. In the United States Constitution, the powers of the federal government granted to Congress are enumerated in Article I, Section 8. Specific powers granted to the Executive Branch are listed in Article II, Section 2. Specific powers granted to the Judicial Branch are listed in Article III, Section 2. In addition, Article VI specifies that the U.S. Constitution, U.S. laws made in accordance with the Constitution, and legally established treaties shall be "the supreme law of the land," binding upon state judges, regardless of what state laws of constitutions might say to the contrary.
Powers reserved for state governments. The United States Constitution also guarantees powers for the states. It does not actually spell out those powers, but, according to Amendment X, "The powers not delegated to the United States by the Constitution, nor prohibited by it to the states, are reserved to the states respectively, or to the people."
Powers denied to the federal government and to state governments. The United States Constitution specifically denied certain powers to the federal government in Article I, Section 9 and also denied certain powers to state governments in Article I, Section 10. After the Constitution was ratified, additional powers of government were denied to the federal government in the Bill of Rights (Amendments I-X). Then, many years later certain restrictions on the powers of state governments were specified in Amendments XIII, XIV, and XV (during the 1850s), and other restrictions were specified during the twentieth century in Amendments XIX, XXIV, and XXVI.