The U.S. Supreme Court case Mississippi Power & Light Co. v. Mississippi ex rel. Moore, Attorney General of Mississippi, et al., 1987 revolved around the issue of whether a state could regulate rates charged by an interstate power company to recover costs associated with its investment in a nuclear power plant located outside the state's boundaries but serving customers within it. The court ruled that while states have authority over retail sales and can set rates for utilities operating within their borders, they cannot use this power to challenge or undermine federal regulations governing wholesale energy markets and interstate commerce in electricity generation resources such as nuclear plants - which fall under federal jurisdiction due to their potential impact on national security and environmental safety standards among other factors considered by agencies like the Nuclear Regulatory Commission (NRC). Therefore, even though some aspects of utility regulation are reserved for states under principles of cooperative federalism embodied in laws like Public Utility Regulatory Policies Act (PURPA), these do not extend to areas preempted by Congress or delegated exclusively to federal authorities.

In the dissenting opinion for Mississippi Power & Light Co. v. Mississippi ex rel. Moore, Justice Scalia argued that the majority's decision to allow state courts to determine prudence in rate-making cases was a departure from established precedent and an intrusion on federal jurisdiction over nuclear power regulation. He contended that allowing states to decide whether investments were prudent would lead them into areas reserved for federal authorities under the Atomic Energy Act of 1954, such as safety considerations related to nuclear power plants or their economic viability compared with other energy sources. Furthermore, he expressed concern about potential inconsistencies between different state rulings and those of federal agencies like the Nuclear Regulatory Commission (NRC). In his view, this could undermine national uniformity in nuclear regulation and create uncertainty for utilities companies considering investing in nuclear facilities.