The International Labor Defense (ILD) (1925–1947) was a legal advocacy organization established in 1925 in the United States as the American section of the Comintern's International Red Aid network. The ILD defended Sacco and Vanzetti, was active in the anti-lynching, movements for civil rights, and prominently participated in the defense and legal appeals in the cause célèbre of the Scottsboro Boys in the early 1930s. Its work contributed to the appeal of the Communist Party among African Americans in the South. In addition to fundraising for defense and assisting in defense strategies, from January 1926 it published Labor Defender, a monthly illustrated magazine that achieved wide circulation. In 1946 the ILD was merged with the National Federation for Constitutional Liberties to form the Civil Rights Congress, which served as the new legal defense organization of the Communist Party USA. It intended to expand its appeal, especially to African Americans in the South. In several prominent cases in which blacks had been sentenced to death in the South, the CRC campaigned on behalf of black defendants. It had some conflict with former allies, such as the NAACP, and became increasingly isolated. Because of federal government pressure against organizations it considered subversive, such as the CRC, it became less useful in representing defendants in criminal justice cases. The CRC was dissolved in 1956. At the same time, in this period, black leaders were expanding the activities and reach of the Civil Rights Movement. In 1954, in a case managed by the NAACP, the US Supreme Court ruled in Brown v. Board of Education that segregation of public schools was unconstitutional.

The American Civil Liberties Union (ACLU) is an American nonprofit human rights organization founded in 1920. The organization strives "to defend and preserve the individual rights and liberties guaranteed to every person in this country by the Constitution and laws of the United States." The ACLU works through litigation and lobbying and has more than 1,800,000 members as of July 2018, with an annual budget over $300 million. ACLU affiliates are active in all 50 states, Washington, D.C., and Puerto Rico. The ACLU provides legal assistance in cases where it considers civil liberties at risk. Legal support from the ACLU can take the form of direct legal representation or preparation of amicus curiae briefs expressing legal arguments when another law firm is already providing representation.