Section 2 provides for apportionment of membership in the House of Representatives on the basis of the whole state population, excluding Native Americans not taxed. A supplemental provision, intended to protect African-American suffrage but never implemented, allows reduction of the congressional representation of a state if male citizens over 21 years old are forbidden to vote. (The main effective constitutional guarantee of African-American suffrage has been the Fifteenth Amendment (adopted 1870), which forbids the United States or any state to abridge the right to vote on account of race, color, or previous condition of servitude.) Section 3 of the Fourteenth Amendment excludes from political office persons who, having sworn to uphold the U.S. Constitution (e.g., army officers and members of Congress) violate this oath, as in the case of those who aided the Confederacy in the Civil War; Congress can remove this disability by a two-thirds vote of each house. Section 4 confirms the public debt but makes void all claims arising from credit extended to the Confederacy or from the loss of slaves. By Section 5, Congress is empowered to enact legislation enforcing the foregoing sections.