Section 1

The right of citizens of the United States, who are eighteen years of age or older, to vote shall not be denied or abridged by the United States or by any State on account of age.

Section 2

The Congress shall have power to enforce this article by appropriate legislation.

By the time of the Vietnam Conflict, most states still limited the franchise to people 21 and older. Because so many men between 18 and 20 were being drafted to fight in Vietnam, Congress came under substantial pressure to expand the franchise to them. Congress consequently enacted the Voting Rights Act of 1970, which lowered the voting age to 18 for all federal, state, and local elections.

In Oregon v. Mitchell (1970), a deeply divided Supreme Court held that Congress had authority to lower the voting age in federal elections, but lacked power to do so for state and local elections. Thus, states were statutorily required to allow people between 18 and 20 to vote for President, U.S. Senate, and the U.S. House of Representatives, but retained discretion to limit state and local elections to voters who were at least 21. In response to Oregon,

To raise and support Armies, but no Appropriation of Money to that Use shall be for a longer Term than two Years;

To provide and maintain a Navy;

To make Rules for the Government and Regulation of the land and naval Forces;

To provide for calling forth the Militia to execute the Laws of the Union, suppress Insurrections and repel Invasions;

To provide for organizing, arming, and disciplining, the Militia, and for governing such Part of them as may be employed in the Service of the United States, reserving to the States respectively, the Appointment of the Officers, and the Authority of training the Militia according to the discipline prescribed by Congress;