The U.S. Supreme Court case Federal Power Commission v. Union Electric Co., 1964, revolved around the issue of whether or not the Federal Power Commission (FPC) had jurisdiction over a hydroelectric project built by Union Electric Company on the Osage River in Missouri. The FPC claimed it did have authority under Section 23(b) of the Federal Power Act because part of that river was navigable waters and thus fell under federal control for purposes related to power generation projects. However, Union Electric argued that since their dam didn't affect interstate commerce directly, it should be exempt from FPC's regulation. In its decision, the Supreme Court sided with FPC stating that Congress intended to give comprehensive authority to regulate all aspects related to hydroelectric projects affecting navigable waters even if they do not directly engage in interstate commerce but could potentially impact it indirectly through controlling water flows or electricity production which can cross state lines.

In the dissenting opinion for Federal Power Commission v. Union Electric Co., Justice Harlan argued that the majority's decision to uphold federal jurisdiction over a hydroelectric project, located on a non-navigable tributary of a navigable river, was an unwarranted expansion of federal power. He contended that this interpretation went beyond what Congress intended when it passed the Federal Power Act and could potentially lead to unlimited intrusion into areas traditionally regulated by states. Furthermore, he disagreed with the majority's reliance on evidence about how electricity is transmitted across state lines as justification for asserting federal control over all aspects of electric power production. Instead, he believed that each case should be evaluated individually based on its specific circumstances rather than applying such broad principles universally.