In American politics and constitutional law, states' rights are guaranteed by the Tenth Amendment to the United States Constitution, (i.e. the tenth article of the Bill of Rights). It is usually used to defend a state law that the Federal government seeks to override, or a perceived violation of the bounds of Federal authority. "States' Rights" is actually a misnomer; only the people, in American constitutional law, hold rights. Governments hold "powers" or "authority."

The principle of federal powers over those powers held by the states was laid out by John Marshall, the first Chief Justice of the Supreme Court of the United States. In the seminal case of McCulloch v. Maryland, Marshall asserted, based on the supremacy clause of the United States Constitution, that the laws of the federal government were generally paramount over the laws of the separate state governments.

The civil rights movement

During the civil rights movement of the 1950s and 1960s, states' rights again become strongly associated with Southern racial politics, with proponents of racial segregation and Jim Crow laws denouncing federal interference in these state-level policies. In 1948, pro-segregationist Strom Thurmond broke with the Democratic Party and formed the States' Rights Democratic Party, also known as the "Dixiecrats". Some observers pointed out that a plausible solution to the dilemma posed by "civil rights" vs. "states' rights" would have been the passage of civil-rights laws on a state rather than a federal level; when few if any such laws were actually introduced during this time (though many were proposed, and passed, later), critics proclaimed the states' rights movement to be a smoke screen for continuing racial discrimination and segregation.

Contemporary debates

The extent of states' rights remains a hotly-debated topic to this day. The use (or non-use) of the death penalty is currently decided by individual states. Other controversial subjects entering the states' rights debate include the authority to legalize assisted suicide, the authority to legalize gay marriage, and the authority to legalize medical marijuana, the last of which is in direct contravention of current federal U.S. law. Another concern is the fact that on more than one occasion, the Federal Government has threatened to withhold highway funds from states unless state governments pass certain articles of legislation. Critics of such actions feel that when the Federal Government does this they upset the balance between the state and Federal governments.

The most important intellectual offspring of the States' Rights philosophy was born in the mind of President Woodrow Wilson, himself sympathetic to Southern ideas (his Southern ancestry and love of the movie The Birth of a Nation bear out this point). His belief in 'self-determination' was a natural outgrowth of States rights ideas, just as W.E.B. DuBois's idea of a new African-American culture grew out of his thesis on Jefferson Davis. Hence, States' Rights is an important Constitutional idea with historical and cultural relevance. States' Rights, Local control, and self-determination are concepts which relate to which level of government is to be preferred. A population can be divided and subdivided down to units of one person, and the conflict of a Federal Government, State governments, and even lesser local governments is one that will continue to excite political leaders and voters as long as political power is divided. Many argue that a healthy tension between local and national power is another healthy check or balance in the totality of government in the United States, in order to diversify democratic powers and preserve minority rights, property rights, civil rights, and other rights.