In Hamm v. City of Rock Hill, the U.S. Supreme Court ruled in favor of African American protesters who had been arrested for trespassing while participating in sit-ins at segregated businesses in South Carolina. The court held that the Civil Rights Act of 1964 nullified any state convictions related to racial segregation protests, even if those convictions occurred prior to the passage of the act. This decision was based on a provision within the Civil Rights Act which banned racial discrimination in places of public accommodation and effectively made it illegal for states to enforce segregation laws through arrests or other punitive measures against peaceful protesters challenging such laws.

In the dissenting opinion for Hamm v. City of Rock Hill, Justice Harlan argued that the majority's decision to void all convictions related to sit-in protests was an overreach of judicial power. He believed it was not within the Supreme Court’s jurisdiction to interfere with state court decisions unless there were clear constitutional violations involved. Harlan asserted that these cases should be handled individually and on their own merits rather than being broadly dismissed as a group. Furthermore, he expressed concern about potential implications this ruling could have on states' rights and federalism principles by undermining local authority in favor of national intervention.