In the United States v. Mississippi et al., 1964, the U.S Supreme Court addressed a case concerning racial discrimination in voter registration in Mississippi. The federal government argued that the state's literacy tests and other requirements were designed to prevent African Americans from voting, thus violating the Fifteenth Amendment of the Constitution which prohibits denying citizens their right to vote based on race or color. The State of Mississippi defended its practices by arguing they were necessary for maintaining an informed electorate and did not intentionally discriminate against any group. However, after reviewing evidence showing stark disparities between white and black voter registration rates along with historical context suggesting discriminatory intent behind these policies, the court ruled unanimously against Mississippi. It held that both state governments and individual officials could be sued for implementing racially discriminatory voting laws under section 601(b) of Title VI of Civil Rights Act (42 U.S.C §2000d). This landmark decision played a significant role in dismantling Jim Crow-era restrictions on black suffrage across Southern states.

In the dissenting opinion for United States v. Mississippi et al., Justice Harlan argued that the majority's decision to strike down Mississippi's voting registration system was an overreach of federal power. He contended that while there were undoubtedly discriminatory practices in place, it was not within the Supreme Court’s jurisdiction to dismantle a state’s entire voter registration process based on these issues. Instead, he believed this responsibility fell upon Congress and should be addressed through legislative means rather than judicial intervention. Furthermore, he expressed concern about setting a precedent where states could potentially lose their rights to manage their own electoral processes due to instances of discrimination or unfairness. Ultimately, Justice Harlan advocated for upholding states' rights and maintaining separation of powers between different branches and levels of government.