In the case of State of Mississippi v. United States in 1990, the Supreme Court ruled on a dispute regarding voting rights and districting. The state of Mississippi had proposed changes to its election laws that would have altered how county supervisors were elected, moving from an at-large system to one based on single-member districts. However, these changes were blocked by the U.S Department of Justice under Section 5 of the Voting Rights Act which requires certain jurisdictions with a history of racial discrimination in voting to obtain federal approval for any change affecting voting. The Supreme Court held that while states are entitled to implement their own electoral systems without undue interference from Congress or other entities, they must still comply with federal law - including those designed to prevent racial discrimination such as Section 5. Therefore, it upheld DOJ's decision blocking Mississippi's proposed changes because they could potentially dilute minority votes and violate this provision.

In the dissenting opinion for the case of State of Mississippi v. United States, Justice O'Connor, joined by Chief Justice Rehnquist and Justices White and Scalia, disagreed with the majority's interpretation of Section 5 of the Voting Rights Act. The dissent argued that this section was not intended to give federal authorities veto power over state decisions regarding electoral systems unless those changes were discriminatory in purpose or effect. They contended that there was no evidence showing Mississippi’s switch from a multi-member district system to a single-member one had such intent or result. Instead, they believed it could enhance minority voting strength by allowing minorities to elect representatives in districts where they form a majority. Therefore, according to them, blocking this change exceeded Congress' enforcement powers under the Fifteenth Amendment and violated principles of federalism enshrined in Tenth Amendment as well as Article IV's guarantee clause which ensures each state shall have a republican form of government.