The State of South Dakota built a cement plant to deal with cement shortages within the state. The South Dakota Cement Commission (the Commission) concluded that all of the cement produced would be needed inside the state. Nevertheless, the plant’s output exceeded South Dakota customers’ needs for many years, and the plant was able to supply cement to both in-state and out-of-state contractors. Later a boom in the construction industry coincided with internal difficulties at the plant. As a result, the plant was unable to fill all of its cement orders. To combat this problem, the Commission reaffirmed that the plant should preferentially supply cement to South Dakota contractors first before filling orders with out-of-state contractors. Reeves, Inc. (Reeves) (plaintiff) was an out-of-state contractor who suffered serious financial harm when the plant stopped filling its orders. Reeves sued the Commission and its chairman, William Stake (collectively, defendants), in district court, challenging the state’s cement sales policy. Reeves argued that the policy unconstitutionally discriminated against interstate commerce in violation of the Commerce Clause. The district court agreed and enjoined the Commission from continuing its preferential treatment of in-state buyers, but the court of appeals reversed. The United States Supreme Court granted certiorari.