The 9th and 10th Amendments close out the Bill of Rights by drawing two different boundaries around government. The Ninth says that just because the Constitution lists certain rights, no one should conclude those are the only rights people have. The Tenth says that any power the Constitution didn’t hand to the federal government stays with the states or with the people. One protects unlisted individual freedoms; the other protects the structural line between Washington and the states. Both have shaped major Supreme Court decisions on privacy, sports gambling, gun regulation, healthcare, and more.
What the Ninth Amendment Does
The Ninth Amendment is one sentence: listing certain rights in the Constitution should not be read to deny or diminish other rights that the people keep for themselves.1Congress.gov. Ninth Amendment
James Madison put it there to solve a specific problem. When the first Congress debated the Bill of Rights, he worried that spelling out particular freedoms like speech and religion would create a dangerous implication. If the Constitution lists only these rights, future officials might argue that anything left off the list is fair game for government control. The Ninth Amendment is the answer to that worry.
The amendment works as a rule of interpretation rather than a source of specific rights on its own. It tells courts and lawmakers that the Bill of Rights is an open list, not a complete catalog. The Congressional Research Service has described it exactly this way, noting that the amendment “states but a rule of construction” meant to prevent the Bill of Rights from being used to expand federal power into areas never intended.2GovInfo. Constitution of the United States: Analysis and Interpretation – Section: Rights Retained by the People The underlying assumption is that people start with full liberty and surrender only specific portions of it to the government. Whatever wasn’t handed over stays with you, whether the Constitution mentions it or not.
How Courts Have Used the Ninth Amendment
The Ninth Amendment sat mostly unused for over 170 years until the Supreme Court decided Griswold v. Connecticut in 1965. That case struck down a state law banning married couples from using contraception. The majority opinion found a right to privacy in the “penumbras” of several amendments, and Justice Goldberg wrote a concurrence arguing that the Ninth Amendment independently supported the result. Goldberg pointed back to Madison’s original concern, writing that the framers “believed that there are additional fundamental rights, protected from governmental infringement, which exist alongside those fundamental rights specifically mentioned in the first eight constitutional amendments.”3Justia. Griswold v. Connecticut, 381 U.S. 479 Later decisions extended that privacy right to contraception for unmarried people and to other personal decisions about family life.4Legal Information Institute. Privacy
The Supreme Court’s 2022 decision in Dobbs v. Jackson Women’s Health Organization narrowed the path Griswold had opened. The Dobbs majority held that for an unenumerated right to qualify for constitutional protection, it must be “deeply rooted in this Nation’s history and tradition” and “implicit in the concept of ordered liberty.” The Court concluded that abortion failed this test, since it had been criminal in every state for most of American history. Justice Thomas went further in a concurrence, arguing that the entire concept of substantive due process is flawed and that the Court should reconsider prior decisions protecting contraception access, same-sex intimacy, and same-sex marriage.5Supreme Court of the United States. Dobbs v. Jackson Women’s Health Organization
The Dobbs majority said its holding applied only to abortion, not to other recognized privacy rights. But the “deeply rooted in history” standard raises the bar for recognizing any new unenumerated right. If a claimed freedom can’t show centuries of legal support behind it, the current Court is unlikely to protect it under either the Ninth Amendment or the Due Process Clause.
What the Tenth Amendment Does
The Tenth Amendment is equally short: any power not given to the federal government by the Constitution, and not explicitly taken away from the states, belongs to the states or the people.6Congress.gov. U.S. Constitution – Tenth Amendment
Where the Ninth Amendment protects individual liberty against narrow readings of the Bill of Rights, the Tenth Amendment protects the structural division of power between federal and state governments. The federal government can only do what the Constitution authorizes. Everything else is someone else’s job.
The boundary between federal and state authority is one of the most litigated questions in American law. Congress has broad powers under the Commerce Clause, the Spending Clause, and other provisions, and the practical scope of “reserved” state power depends on how narrowly or broadly courts interpret those federal powers. The Tenth Amendment doesn’t list what states can do. It’s a residual clause that catches everything the Constitution doesn’t assign somewhere else.
The Anti-Commandeering Rule
The clearest legal rule to emerge from the Tenth Amendment is that Congress cannot force state governments to carry out federal programs. The Supreme Court established this principle in New York v. United States in 1992, striking down a federal law that required states to either regulate radioactive waste according to federal instructions or take ownership of the waste themselves. The Court held that Congress “may not commandeer the States’ legislative processes by directly compelling them to enact and enforce a federal regulatory program.”7Justia. New York v. United States, 505 U.S. 144
Five years later, Printz v. United States extended the rule to state executive officials. The Court struck down a provision of the Brady Handgun Violence Protection Act that required local law enforcement officers to conduct background checks on handgun buyers. The opinion declared that the federal government “may neither issue directives requiring the States to address particular problems, nor command the States’ officers to administer or enforce a federal regulatory program.”8Legal Information Institute. U.S. Constitution Annotated – Anti-Commandeering Doctrine
The doctrine got its most recent major test in Murphy v. NCAA in 2018, when the Court struck down the Professional and Amateur Sports Protection Act. That federal law prohibited states from authorizing sports gambling. The Court held that telling a state legislature what it may not legalize is just as much commandeering as telling it what it must do: “The distinction between compelling a State to enact legislation and prohibiting a State from enacting new laws is an empty one.”9Supreme Court of the United States. Murphy v. National Collegiate Athletic Association The decision opened the door for states to legalize sports betting on their own terms, and dozens have since done so.
The rule has limits. It doesn’t prevent Congress from regulating individuals directly, and it doesn’t stop the federal government from enforcing its own laws using federal agents. What it prohibits is drafting state officials into federal service.
Where the Commerce Clause Limits Reserved Powers
The biggest practical limit on the Tenth Amendment’s reserved powers comes from the Commerce Clause, which gives Congress authority to regulate interstate commerce. For much of the twentieth century, the Supreme Court read that power so broadly that very little economic activity fell outside federal reach.
That changed in 1995 with United States v. Lopez, where the Court struck down the Gun-Free School Zones Act. Congress had argued that guns near schools affected interstate commerce through a chain of economic reasoning, but the Court rejected that logic, warning that accepting it “would eliminate the distinction between what is truly national and what is truly local” and “would convert Congress’s commerce power into a general police power of the sort retained by the states.”10Congress.gov. Commerce Clause and Tenth Amendment
The boundary is still blurry, though. In Gonzales v. Raich a decade later, the Court upheld Congress’s power to ban homegrown marijuana even in states that had legalized it for medical use. The reasoning: Congress could rationally conclude that failing to regulate locally grown marijuana would “leave a gaping hole” in the federal drug enforcement scheme, because homegrown product is effectively impossible to distinguish from marijuana that crosses state lines.11Justia. Gonzales v. Raich, 545 U.S. 1 Activity that looks purely local can still fall under federal authority if Congress can show a rational connection to the interstate market. Most Commerce Clause disputes today play out somewhere between Lopez and Raich.
Federal Spending as Leverage Over States
When Congress can’t order states to do something, it can often achieve the same result by attaching conditions to federal money. The Spending Clause allows Congress to offer funds on the condition that states follow certain rules. The Supreme Court has drawn a line between persuasion and coercion.
In South Dakota v. Dole (1987), the Court upheld a federal law that withheld 5% of highway funding from states with a drinking age below 21. The Court laid out four requirements for valid spending conditions: the spending must serve the general welfare, conditions must be stated clearly so states know what they’re agreeing to, the conditions must relate to the federal interest in the program, and the conditions can’t violate other constitutional provisions. The 5% withholding amounted to less than half a percent of South Dakota’s total budget, which the Court called “relatively mild encouragement.”12Justia. South Dakota v. Dole, 483 U.S. 203
The line between encouragement and compulsion became clearer in NFIB v. Sebelius (2012), the Affordable Care Act case. Congress told states to expand Medicaid eligibility or lose all their existing Medicaid funding. The Court held this crossed from incentive into coercion. Medicaid funding represented roughly 10% of a typical state’s budget, and the threatened loss left states “with no choice but to accept” the new program.13Justia. National Federation of Independent Business v. Sebelius, 567 U.S. 519 States could accept the Medicaid expansion voluntarily, but Congress couldn’t punish holdouts by revoking existing funds.14Congress.gov. Anti-Coercion Requirement and Spending Clause
The practical takeaway: the federal government routinely shapes state policy through funding conditions on education, transportation, healthcare, and other programs. States technically retain the choice to refuse, but when federal money funds a large share of a state program, that choice can feel more like an ultimatum. Where the constitutional line falls gets drawn case by case.
Federal Preemption and the Supremacy Clause
Even where states hold reserved powers, federal law can override state law through the Supremacy Clause of Article VI, which establishes that the Constitution and federal laws made under it are “the supreme Law of the Land.”15Congress.gov. U.S. Constitution – Article VI When a valid federal law directly conflicts with a state law, the state law gives way. That doesn’t erase the Tenth Amendment. It means reserved powers operate inside a framework where federal authority, properly exercised, takes priority.
Preemption comes in several forms. Congress sometimes explicitly states that a federal law overrides state regulation in a particular area. In other situations, federal regulation is so comprehensive that courts conclude Congress intended to occupy the entire field, leaving no room for state rules. And when state and federal requirements genuinely conflict so that complying with both is impossible, the state law falls. Courts generally presume Congress does not intend to displace state law in areas of traditional state authority, like health and safety regulation, unless the evidence of preemption is clear. That presumption gives the Tenth Amendment’s reserved powers some insulation even when federal law is broad.
What States Do With Their Reserved Powers
The powers the Tenth Amendment reserves to the states are commonly called “police powers,” though the term has nothing to do with law enforcement specifically. It refers to the broad authority states hold to regulate for public health, safety, morals, and general welfare. The Supreme Court has described these traditional applications as covering “public safety, public health, morality, peace and quiet, law and order.”16Legal Information Institute. Police Powers
In everyday life, this means states and local governments handle most of the regulation that directly affects you:
- Public health: hospital oversight, vaccination requirements, disease reporting, restaurant inspections, and drinking water standards.
- Public safety: criminal law enforcement, fire codes, building inspections, and traffic regulation.
- Education: school districts, curriculum standards, teacher certification, and compulsory attendance rules.
- Professional licensing: doctors, lawyers, electricians, real estate agents, and many other occupations require state-issued licenses.
- Land use: zoning laws, property taxes, building permits, and local environmental review.
- Elections: voter registration, polling locations, ballot design, and most election administration.
The federal government holds no general police power. It can regulate only where the Constitution gives it authority, primarily through the Commerce Clause, taxing power, and spending power.16Legal Information Institute. Police Powers Everything else defaults to the states. That’s why a state can set its own speed limits, define its own crimes, and license its own professionals without asking Congress for permission. The Tenth Amendment doesn’t grant these powers. It recognizes that the states never gave them up.