Supreme Court Leaves Door Open to State-Law-Based Tort Liability for Nuclear Licensees

• The Supreme Court declined to review the Eighth Circuit’s decision in Mazzocchio v. Cotter Corp., even the though the United States had advised the Court that the case had been incorrectly decided. 
• The denial of certiorari permits a circuit split to continue and subjects Eighth Circuit licensees to potential liability for nuclear incidents even where they have complied with NRC or DOE requirements. 
• Licensees in Third, Seventh, and Eleventh Circuits can find safe harbor from tort liability where they adhere to federal licensing and regulatory obligations.
• Liability exposure is no longer uniform and will depend on geography, litigation posture, and how courts continue to interpret the interaction between federal and state law. 

On May 18, 2026, the Supreme Court denied a petition for a writ of certiorari in Cotter Corp. v. Mazzocchio. Adhering to the recommendation of the Solicitor General, the Court declined to review the Eighth Circuit’s determination that plaintiffs, sisters exposed to radiation from radioactive source material stored at a site owned by defendants, could bring a “public liability action” under the Price-Anderson Act based on standards of care derived from state law. The Eighth Circuit had rejected the conclusion of three other circuits that federal law provides the exclusive source of nuclear-safety standards of care in public liability actions, thus creating a circuit split. The Solicitor General advised the Supreme Court that the Eighth Circuit’s view was incorrect but recommended that the Court deny review because of its view that further “percolation” of the issue is warranted.  The Nuclear Energy Institute urged the Court to review the Eighth Circuit’s decision. 

The issue in Cotter stems from amendments to the Price-Anderson Act that Congress passed in 1988 following the accident at Three Mile Island. The amendments granted district courts original jurisdiction to entertain a “public liability action,” 42 U.S.C. § 2210(n)(2), defined to mean a suit asserting “public liability,” i.e., “any legal liability arising out of or resulting from a nuclear incident or precautionary evacuation.”  

Congress further instructed in the 1988 amendments that 

[a] public liability action shall be deemed to be an action arising under section 2210 of this title, and the substantive rules for decision in such action shall be derived from the law of the State in which the nuclear incident involved occurs, unless such law is inconsistent with the provisions of such section. 

The plaintiffs in Cotter filed a public liability action in district court in Missouri raising a challenge based on both state and federal standards of care, including claims under state law for negligence, negligence per se, strict liability, and civil conspiracy. Plaintiffs contended that they could succeed on their state-law claims even if the defendants acted in accordance with NRC requirements, i.e., even if the levels of radioactivity at the underlying site were consistent with federal law.

The Eighth Circuit, considering the issue as a certified question on an interlocutory basis, ruled that state tort law was not preempted by the Atomic Energy Act, even if the effect of its ruling would be to indirectly regulate federally licensed facilities. The court distinguished between state efforts to engage in before-the-fact regulation of NRC licensees—which it recognized as being preempted under the Supreme Court’s decision in Pacific Gas & Electric Co. v. State Energy Resource Conservation and Development Commission and 42 U.S.C. § 2021(b)—and after-the-fact regulation through imposition of tort liability—which it deemed to be consistent with the Supreme Court’s decision in Silkwood v. Kerr-McGee Corp. And it observed that in 42 U.S.C. 2014(ii) Congress directed that federal courts should apply state law substantive rules for decision—including state tort law—in public liability actions.  The court further determined that nothing in the state’s tort law was inconsistent with 42 U.S.C. § 2210. 

The Eighth Circuit acknowledged that its conclusion differed from that of other federal courts. And the Solicitor General explained that the Third, Seventh, and Eleventh Circuits had “squarely addressed the question presented and . . . held that, because the federal government has occupied the field of nuclear-safety concerns, federal law provides the exclusive source of the nuclear-safety standards of care that apply in PAA public liability actions.”  The Solicitor General clarified that, consistent with 42 U.S.C.§ 2014(ii), state law can provide the “infrastructure” (such as the elements of the claims) for adjudicating tort claims in public liability actions, but that the standard of care itself should be defined by federal law. He also noted that the rules need only be “derived from” state law, and not actually directly incorporate state law.

What the Circuit Split Means

The Supreme Court’s decision leaves a meaningful and unresolved split among federal courts.

Lower Risk Jurisdictions

In the Third, Seventh, and Eleventh Circuits:

• Licensees can generally rely on regulatory compliance.
• Meeting NRC or DOE requirements provides a strong defense to liability.

Higher Risk Jurisdictions

In the Eighth Circuit, which includes Arkansas, Iowa, Minnesota, Nebraska, North Dakota, and South Dakota:

• Licensees may face liability even when fully compliant with federal law.
• Plaintiffs may argue that state law imposes more demanding standards.

What This Means for Nuclear Licensees

This decision has practical implications for nuclear operators and investors.

Compliance alone may not be sufficient

Meeting federal regulatory requirements remains essential but may not fully protect against liability in all jurisdictions.

Risk now varies by jurisdiction

Exposure depends on where claims are brought, increasing uncertainty for operators with multi-state activities.

State tort law is a growing risk factor

Even in a heavily regulated industry, state law may influence outcomes in litigation.

Preemption defenses are less predictable

Operators can no longer assume that federal law will fully displace state law claims.

Practical Considerations

In this environment, licensees should consider:

• Reassessing litigation exposure under the Price-Anderson Act.
• Evaluating jurisdiction-specific risks across their operations.    
• Reviewing whether operational practices exceed minimum federal standards where risk exposure is highest.  
• Monitoring appellate developments and the potential for future Supreme Court review.    
• Engaging in policy discussions as the legal framework continues to evolve.

Bottom Line

The Supreme Court’s decision leaves unresolved a fundamental question about whether federal law exclusively governs nuclear safety standards in Price-Anderson litigation. For now, nuclear licensees face a fragmented legal landscape. In some jurisdictions, compliance with federal law provides meaningful protection. In others, it may not. As a result, liability exposure is no longer uniform and will depend on geography, litigation posture, and how courts continue to interpret the interaction between federal and state law.