The case of Hancock, Attorney General of Kentucky v. Train, Administrator, Environmental Protection Agency (EPA), et al., 1975 revolved around the interpretation of the Clean Air Act and its application to state facilities. The EPA had issued a regulation requiring states to adopt and submit plans for implementing emission standards at all stationary sources within their jurisdiction including state-owned facilities. Kentucky objected to this rule arguing that it violated principles of federalism by infringing on state sovereignty as it required them to regulate their own establishments which they believed was not mandated by the Clean Air Act. The Supreme Court ruled in favor of Kentucky stating that while Congress intended for states to have broad responsibilities under the act's implementation plan provisions, there was no clear directive from Congress authorizing direct federal regulation over state facilities without explicit consent from each individual State. Therefore, according to statutory construction rules where ambiguity exists regarding intrusion into traditional areas of State power such as control over property and personnel within its domain - a more restrictive interpretation is appropriate unless Congress has unmistakably made known its intent otherwise.

In the dissenting opinion for Hancock v. Train, Justice William Rehnquist argued that the Environmental Protection Agency (EPA) did not have authority to require states to obtain permits for air pollution sources owned or operated by a state or local agency under Section 118 of the Clean Air Act. He contended that this interpretation was inconsistent with other sections of the Act and exceeded Congress's intent in passing it. Rehnquist believed that if Congress had intended such an expansive role for federal regulation over state facilities, they would have explicitly stated so within the legislation itself. Furthermore, he expressed concern about potential infringement on states' rights and sovereignty due to excessive federal oversight and control.