Federalism refers to the division of policymaking authority between the federal government and:

The Constitution contains several provisions that direct the functioning of U.S. federalism. Some delineate the scope of national and state power, while others restrict it. The remaining provisions shape relationships among the states and between the states and the federal government.

The enumerated powers of the national legislature are found in Article I, Section 8. These powers define the jurisdictional boundaries within which the federal government has authority. In seeking not to replay the problems that plagued the young country under the Articles of Confederation, the Constitution’s framers granted Congress specific powers that ensured its authority over national and foreign affairs. To provide for the general welfare of the populace, it can tax, borrow money, regulate interstate and foreign commerce, and protect property rights, for example. To provide for the common defense of the people, the federal government can raise and support armies and declare war. Furthermore, national integration and unity are fostered with the government’s powers over the coining of money, naturalization, postal services, and other responsibilities.

The last clause of Article I, Section 8, commonly referred to as the elastic clause or the necessary and proper cause, enables Congress “to make all Laws which shall be necessary and proper for carrying” out its constitutional responsibilities. While the enumerated powers define the policy areas in which the national government has authority, the elastic clause allows it to create the legal means to fulfill those responsibilities. However, the open-ended construction of this clause has enabled the national government to expand its authority beyond what is specified in the Constitution, a development also motivated by the expansive interpretation of the commerce clause, which empowers the federal government to regulate interstate economic transactions.

The powers of the state governments were never listed in the original Constitution. The consensus among the framers was that states would retain any powers not prohibited by the Constitution or delegated to the national government.Jack Rakove. 2007. James Madison and the Creation of the American Republic. New York: Pearson; Samuel H. Beer. 1998. To Make a Nation: The Rediscovery of American Federalism. Cambridge, MA: Harvard University Press. However, when it came time to ratify the Constitution, a number of states requested that an amendment be added explicitly identifying the reserved powers of the states. What these Anti-Federalists sought was further assurance that the national government’s capacity to act directly on behalf of the people would be restricted, which the first ten amendments (Bill of Rights) provided. The Tenth Amendment affirms the states’ reserved powers: “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.” Indeed, state constitutions had bills of rights, which the first Congress used as the source for the first ten amendments to the Constitution.

Some of the states’ reserved powers are no longer exclusively within state domain, however. For example, since the 1940s, the federal government has also engaged in administering health, safety, income security, education, and welfare to state residents. The boundary between intrastate and interstate commerce has become indefinable as a result of broad interpretation of the commerce clause. Shared and overlapping powers have become an integral part of contemporary U.S. federalism. These concurrent powers range from taxing, borrowing, and making and enforcing laws to establishing court systems (Figure).Elton E. Richter. 1929. “Exclusive and Concurrent Powers in the Federal Constitution,” Notre Dame Law Review 4, No. 8: 513–542. http://scholarship.law.nd.edu/cgi/viewcontent.cgi?article=4416&context=ndlr

Article I, Sections 9 and 10, along with several constitutional amendments, lay out the restrictions on federal and state authority. The most important restriction Section 9 places on the national government prevents measures that cause the deprivation of personal liberty. Specifically, the government cannot suspend the writ of habeas corpus, which enables someone in custody to petition a judge to determine whether that person’s detention is legal; pass a bill of attainder, a legislative action declaring someone guilty without a trial; or enact an ex post facto law, which criminalizes an act retroactively. The Bill of Rights affirms and expands these constitutional restrictions, ensuring that the government cannot encroach on personal freedoms.

The states are also constrained by the Constitution. Article I, Section 10, prohibits the states from entering into treaties with other countries, coining money, and levying taxes on imports and exports. Like the federal government, the states cannot violate personal freedoms by suspending the writ of habeas corpus, passing bills of attainder, or enacting ex post facto laws. Furthermore, the Fourteenth Amendment, ratified in 1868, prohibits the states from denying citizens the rights to which they are entitled by the Constitution, due process of law, or the equal protection of the laws. Lastly, three civil rights amendments—the Fifteenth, Nineteenth, and Twenty-Sixth—prevent both the states and the federal government from abridging citizens’ right to vote based on race, sex, and age. This topic remains controversial because states have not always ensured equal protection.

The supremacy clause in Article VI of the Constitution regulates relationships between the federal and state governments by declaring that the Constitution and federal law are the supreme law of the land. This means that if a state law clashes with a federal law found to be within the national government’s constitutional authority, the federal law prevails. The intent of the supremacy clause is not to subordinate the states to the federal government; rather, it affirms that one body of laws binds the country. In fact, all national and state government officials are bound by oath to uphold the Constitution regardless of the offices they hold. Yet enforcement is not always that simple. In the case of marijuana use, which the federal government defines to be illegal, twenty-three states and the District of Columbia have nevertheless established medical marijuana laws, others have decriminalized its recreational use, and four states have completely legalized it. The federal government could act in this area if it wanted to. For example, in addition to the legalization issue, there is the question of how to treat the money from marijuana sales, which the national government designates as drug money and regulates under laws regarding its deposit in banks.

Various constitutional provisions govern state-to-state relations. Article IV, Section 1, referred to as the full faith and credit clause or the comity clause, requires the states to accept court decisions, public acts, and contracts of other states. Thus, an adoption certificate or driver’s license issued in one state is valid in any other state. The movement for marriage equality has put the full faith and credit clause to the test in recent decades. In light of Baehr v. Lewin, a 1993 ruling in which the Hawaii Supreme Court asserted that the state’s ban on same-sex marriage was unconstitutional, a number of states became worried that they would be required to recognize those marriage certificates.Baehr v. Lewin. 1993. 74 Haw. 530. To address this concern, Congress passed and President Clinton signed the Defense of Marriage Act (DOMA) in 1996. The law declared that “No state (or other political subdivision within the United States) need recognize a marriage between persons of the same sex, even if the marriage was concluded or recognized in another state.” The law also barred federal benefits for same-sex partners.

DOMA clearly made the topic a state matter. It denoted a choice for states, which led many states to take up the policy issue of marriage equality. Scores of states considered legislation and ballot initiatives on the question. The federal courts took up the issue with zeal after the U.S. Supreme Court in United States v. Windsor struck down the part of DOMA that outlawed federal benefits.United States v. Windsor, 570 U.S. __ (2013). That move was followed by upwards of forty federal court decisions that upheld marriage equality in particular states. In 2014, the Supreme Court decided not to hear several key case appeals from a variety of states, all of which were brought by opponents of marriage equality who had lost in the federal courts. The outcome of not hearing these cases was that federal court decisions in four states were affirmed, which, when added to other states in the same federal circuit districts, brought the total number of states permitting same-sex marriage to thirty.Adam Liptak, “Supreme Court Delivers Tacit Win to Gay Marriage,” New York Times, 6 October, 2014. Then, in 2015, the Obergefell v. Hodges case had a sweeping effect when the Supreme Court clearly identified a constitutional right to marriage based on the Fourteenth Amendment.Obergefell v. Hodges, 576 U.S. ___ (2015).

The privileges and immunities clause of Article IV asserts that states are prohibited from discriminating against out-of-staters by denying them such guarantees as access to courts, legal protection, property rights, and travel rights. The clause has not been interpreted to mean there cannot be any difference in the way a state treats residents and non-residents. For example, individuals cannot vote in a state in which they do not reside, tuition at state universities is higher for out-of-state residents, and in some cases individuals who have recently become residents of a state must wait a certain amount of time to be eligible for social welfare benefits. Another constitutional provision prohibits states from establishing trade restrictions on goods produced in other states. However, a state can tax out-of-state goods sold within its borders as long as state-made goods are taxed at the same level.