The U.S. Supreme Court case ETSI Pipeline Project v. Missouri et al., 1987, revolved around a dispute over the construction of a coal slurry pipeline by Energy Transportation Systems, Inc (ETSI). The state of Missouri and several other states challenged the project on grounds that it violated their rights under the Commerce Clause and Supremacy Clause of the Constitution. They argued that they had not been given adequate opportunity to participate in regulatory proceedings related to water allocation for this interstate project. The court ruled in favor of ETSI stating that while states have legitimate interests in controlling water within their borders, these interests do not override federal authority when it comes to regulating interstate commerce or preempting state law with federal legislation. Therefore, even though some aspects of water regulation may fall under state jurisdiction, decisions about large-scale projects like pipelines crossing multiple states are ultimately subject to federal control.

The dissenting opinion in the ETSI Pipeline Project v. Missouri case argued that the majority's decision was a departure from established precedent regarding interstate commerce regulation. The dissenters believed that Congress had clear authority to regulate interstate commerce, and this included approving projects like the pipeline proposed by ETSI. They contended that states should not have veto power over such projects as it could lead to parochial decisions contrary to national interests. Furthermore, they disagreed with the majority's interpretation of "commerce" under Article I, Section 8 of Constitution; arguing instead for a broader understanding which would encompass activities having substantial relation to interstate commerce - including transportation infrastructure like pipelines.