Johnson implemented his own form of Presidential Reconstruction – a series of proclamations directing the seceded states to hold conventions and elections to re-form their civil governments. When Southern states returned many of their old leaders, and passed Black Codes to deprive the freedmen of many civil liberties, Congress refused to seat legislators from those states and advanced legislation to overrule the Southern actions. Johnson vetoed their bills, and Congress overrode him, setting a pattern for the remainder of his presidency. Johnson opposed the Fourteenth Amendment, which gave citizenship to African-Americans. As the conflict between the branches of government grew, Congress passed the Tenure of Office Act, restricting Johnson in firing Cabinet officials. When he persisted in trying to dismiss Secretary of War Edwin Stanton, he was impeached by the House of Representatives, and narrowly avoided conviction in the Senate and removal from office. Returning to Tennessee after his presidency, Johnson sought political vindication, and gained it in his eyes when he was elected to the Senate again in 1875 (the only former president to serve there), just months before his death. Although Johnson's ranking has fluctuated over time, he is generally considered among the worst American presidents for his opposition to federally guaranteed rights for African Americans.