Difficulty: Introductory to Intermediate | Prerequisites: Understanding of enumerated and implied powers (see companion notes).
Federalism is the constitutional arrangement that divides governing authority between the national government and the states. Once you understand what powers the Constitution grants to the federal government (enumerated and implied powers), the next question is: what happens to everything else? The answer is federalism. The Supremacy Clause, the Commerce Clause, and the Tenth Amendment together define which level of government controls what, and what happens when they disagree. This is one of the most tested areas in any American government course.
The Constitution splits power between the federal government and the states. The Supremacy Clause makes federal law the final word when state and federal laws conflict. The Commerce Clause gives Congress authority over interstate and foreign trade, while the Tenth Amendment reserves everything not delegated to the federal government to the states or the people.
Federalism
A system of government in which power is divided between a central (national) authority and constituent political units (states). In the U.S., both levels of government derive their authority from the Constitution.
Think of it as a shared-responsibility arrangement: some things only the federal government can do, some things only the states can do, and some things both can do.
Supremacy Clause (Article VI, Clause 2)
The constitutional provision declaring that the Constitution and federal laws made under it are "the supreme law of the land." When a state law conflicts with a valid federal law, the federal law prevails.
In simple terms, federal law wins whenever it clashes with state law.
Commerce Clause (Article I, Section 8, Clause 3)
Grants Congress the power to regulate commerce "among the several States" and with foreign nations and Native American tribes. This clause has been one of the most significant sources of expanding federal power.
Think of it as the constitutional hook the federal government uses to regulate economic activity that crosses state lines, and, through interpretation, a great deal of activity that affects interstate commerce even indirectly.
Tenth Amendment (reserved powers)
The final amendment in the Bill of Rights, stating: "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."
In simple terms, if the Constitution does not give a power to the federal government and does not ban it for the states, it belongs to the states or to the people.
Reserved powers
Powers retained by the states under the Tenth Amendment. These typically include authority over education, policing, marriage laws, and intrastate commerce.
Think of it as the states' own toolkit: the powers the federal government was never given and therefore cannot claim.
Concurrent powers
Powers shared by both the federal and state governments. Examples include the power to tax, build roads, and establish courts.
In simple terms, some responsibilities belong to both levels of government at once, and both can act on them independently.
Article VI, Clause 2 establishes that the Constitution and valid federal laws are the supreme law of the land
When a state law directly conflicts with a federal law, the state law is invalid (this is called federal preemption)
This principle ensures a uniform legal framework across all states on matters within federal jurisdiction
Without the Supremacy Clause, states could simply ignore federal law, which was precisely the problem under the Articles of Confederation
Article I, Section 8, Clause 3 gives Congress power to regulate interstate and foreign commerce
The Commerce Clause formally assigns trade-related powers to the federal government: foreign commerce, interstate commerce, navigation, navigation laws, and patents
States retain control over intrastate commerce (trade within a single state's borders), provided it does not substantially affect interstate commerce
Over time, the Commerce Clause has been interpreted broadly, becoming one of the primary vehicles for expanding federal regulatory authority
Key principle: the federal government handles matters that cross state lines; states handle matters that stay within their borders
The Tenth Amendment draws a clear boundary: powers not given to the federal government and not prohibited to the states are reserved to the states or the people
Reserved powers include education policy, law enforcement, family law, and local government structure
The Tenth Amendment was included to reassure states that ratifying the Constitution would not mean surrendering all authority to a central government
It functions as the constitutional counterweight to the Supremacy Clause and the Necessary and Proper Clause
The Constitution creates a layered system: some powers belong exclusively to the federal government (e.g., declaring war, coining money), some exclusively to the states (e.g., issuing licences, running elections), and some are shared (concurrent powers such as taxation)
When both levels of government act in the same area, the Supremacy Clause determines which prevails in a conflict
The overall design aims for harmony between levels of government, with each operating within its defined sphere
The Commerce Clause is why the federal government can regulate things like airline safety, food labelling, and environmental standards: all of these involve goods or services that move across state lines. When you see a federal regulation that seems to reach into local business, the Commerce Clause is almost always the constitutional basis.
The Tenth Amendment is why education policy varies so dramatically from state to state. There is no federal right to education in the Constitution, so states set their own curricula, standards, and funding models.
Students often think the Supremacy Clause means the federal government can do anything it wants. It does not. Federal law is supreme only within the scope of the federal government's constitutional authority. A federal law that exceeds that authority can be struck down.
Students sometimes confuse reserved powers with concurrent powers. Reserved powers belong exclusively to the states (e.g., issuing driving licences). Concurrent powers are shared by both levels (e.g., taxation).
Students frequently assume the Commerce Clause has always been interpreted broadly. For much of American history, it was read narrowly. The broad interpretation is largely a twentieth-century development.
Students sometimes believe the Tenth Amendment gives states the power to override federal law. It does not. It only reserves powers that the Constitution has not already assigned to the federal government.
⚠️ Know the Supremacy Clause by its location (Article VI, Clause 2) and be able to explain its effect: federal law overrides conflicting state law.
⚠️ The Commerce Clause (Article I, Section 8, Clause 3) is one of the most commonly tested provisions. Be prepared to explain both what it grants and how its interpretation has expanded over time.
⚠️ Be able to state the Tenth Amendment from memory, or close to it. Exams frequently ask students to explain the principle of reserved powers.
⚠️ Understand the difference between exclusive federal powers, exclusive state powers, and concurrent powers, and be ready to give examples of each.
⚠️ If your course covers case law, expect questions linking federalism principles to cases such as McCulloch v. Maryland (1819) or Gibbons v. Ogden (1824).
True or false: The Supremacy Clause means state law always takes priority over federal law. (False. Federal law takes priority when the two conflict.)
Fill in the blank: The _______ Clause gives Congress the power to regulate commerce among the states and with foreign nations. (Commerce Clause.)
True or false: The Tenth Amendment reserves all powers not delegated to the federal government to the states or the people. (True.)
Fill in the blank: Powers shared by both federal and state governments, such as the power to tax, are called _______ powers. (Concurrent powers.)
True or false: Education policy is primarily a federal power under the Constitution. (False. Education is a reserved power of the states under the Tenth Amendment.)
Q: What is the Supremacy Clause, and why was it included in the Constitution?
A: The Supremacy Clause (Article VI, Clause 2) declares that the Constitution and federal laws are the supreme law of the land. It was included to prevent states from disregarding federal authority, a problem that had undermined the Articles of Confederation.
Q: How does the Commerce Clause divide economic authority between the federal and state governments?
A: The Commerce Clause (Article I, Section 8, Clause 3) gives Congress exclusive authority over foreign and interstate commerce, including trade, navigation, and patents. States retain authority over intrastate commerce, provided their regulations do not conflict with or substantially burden interstate trade.
Q: What does the Tenth Amendment protect, and why does it matter?
A: The Tenth Amendment reserves all powers not delegated to the federal government (and not prohibited to the states) to the states or the people. It matters because it sets a constitutional boundary on federal expansion: any power not in the Constitution belongs to the states or the people by default.
Q: Give two examples each of exclusive federal powers, exclusive state powers, and concurrent powers.
A: Exclusive federal powers: declaring war, coining money. Exclusive state powers: issuing drivers' licences, establishing local governments. Concurrent powers: levying taxes, building roads.
Q: What happens when a state law conflicts with a valid federal law?
A: Under the Supremacy Clause, the federal law prevails. The state law is considered invalid to the extent it conflicts with the federal law. This principle is known as federal preemption.
This material builds directly on the enumerated and implied powers covered in the companion study notes. The Necessary and Proper Clause and the Commerce Clause work together: Congress uses the Commerce Clause to identify its authority and the Elastic Clause to extend it.
Federalism also connects to any unit on the Civil War and Reconstruction, where the balance of federal and state power was the central political and constitutional question.
If your course covers landmark Supreme Court cases, Gibbons v. Ogden (1824) is the key Commerce Clause case, and McCulloch v. Maryland (1819) addresses both implied powers and federal supremacy over the states.
Federalism, Supremacy Clause, Article VI, Commerce Clause, Article I Section 8 Clause 3, Tenth Amendment, reserved powers, concurrent powers, exclusive powers, federal preemption, interstate commerce, intrastate commerce, division of powers, state sovereignty, dual federalism, cooperative federalism, federal vs state authority, Constitutional History to 1865, Gibbons v. Ogden, McCulloch v. Maryland