In the case of South Dakota v. Nebraska et al., 1981, the Supreme Court was asked to resolve a dispute over water rights between several states. The issue at hand involved an interpretation of the Missouri River Compact, an agreement that allocated certain amounts of river water to each state for their use. South Dakota claimed that Nebraska and other downstream states were using more than their fair share, thereby depriving them of needed resources. The Supreme Court ruled in favor of Nebraska and its co-defendants by upholding a lower court's decision which found no violation on part of these states regarding usage limits set by the compact. The court held that while there may be fluctuations in how much water each state uses from year to year due to factors like rainfall or droughts, this did not constitute a breach as long as average consumption remained within agreed-upon bounds. This ruling underscored principles about interstate compacts and resource allocation among U.S. states; it also emphasized respect for agreements made between sovereign entities under federal law.

In the dissenting opinion for South Dakota v. Nebraska et al., Justice Harry Blackmun argued that the majority's decision to deny South Dakota its equitable apportionment claim was unjustified. He contended that the Court had failed to consider all relevant factors, particularly those related to conservation and reasonable use of water resources. Blackmun believed that by focusing solely on historical usage patterns, without considering whether these were sustainable or fair, the Court had effectively rewarded wasteful practices at South Dakota's expense. He also criticized their failure to properly apply legal principles established in previous cases dealing with interstate water disputes. In his view, this resulted in an inequitable distribution of shared resources between states and set a dangerous precedent for future decisions.