Can States Still Protect Public Health? The Risk of a Climate Regulatory Vacuum

On Oct. 5, 2026, the U.S. Supreme Court heard oral arguments in a case that has the potential to greatly impact state and local municipalities’ ability to fight widespread threats to public and environmental health. For more than eight years Boulder County, Colorado, has been locked in a protracted legal battle with prominent energy companies that produce, refine and market fossil fuels. The litigation, now Suncor Energy (U.S.A) Inc. v. County Commissioners of Boulder County, seeks to recover monetary relief to compensate the Plaintiff — Boulder County — for their past and future damages and costs related to mitigating the impact of climate change. 

The case began in 2018 when Boulder County first filed its complaint against defendants, Exxon Mobil and Suncor (fossil fuel companies). Initially, the case bounced between state and federal court as judges grappled with venue challenges, leading to a recurring question about in which jurisdiction the case should be tried. Eventually, in 2023, the venue question was resolved when the Supreme Court denied the fossil fuel companies’ request to hear an appeal of the U.S. Court of Appeals for the Tenth Circuit’s decision remanding the case to state court where it was originally filed.

However, the fossil fuel companies were quick to present new challenges, this time based on preemption. But both the state trial court and Colorado’s Supreme Court rejected defendant’s contention. 

Preemption, the concept that a higher level of government may limit or even eliminate the powers of a lower level of government, is a legal doctrine that on the federal level rests on the Supremacy Clause of the Constitution, which establishes federal supremacy over state law. Although preemption has been broadly used across the country and across party lines, in the last few years it has been used frequently by industry and in lockstep with the Trump Administration’s deregulatory agenda to weaken the ability of state and local governments to protect the health of their residents. 

Suncor does not map cleanly on the traditional areas of preemption found in Supreme Court precedent. Typically, the Supreme Court has held that preemption can either be express, when it is called for in a specific provision in an act, implied from Congressional intent, or as a result of a conflict between state and federal law. The Clean Air Act does not contain any provision expressly preempting state regulation or tort liability for greenhouse-gas emissions, and there is no clear conflict between the federal and state laws in question nor any reason that both laws could not be followed simultaneously.

The fossil fuel companies argue that since pollution has an interstate impact, the states cannot regulate its emissions absent express authorization from Congress. If this argument is accepted by the Court, it could serve as rationale for preempting any state environmental laws or any other regulation not affirmatively authorized by Congress. This could dramatically eviscerate the states’ police power.

Suncor also argues that the states cannot act because the alleged harm relates to foreign affairs as greenhouse-gas emissions are “inherently transboundary.” From this, Suncor concludes that the issue falls within the federal government’s exclusive power over foreign relations. While previous Supreme Court cases like Crosby or Garamendi have found preemption of claims related to foreign affairs, extending that precedent to this case would again dramatically undercut the states’ police power, potentially barring a state from pursuing any civil justice claims for environmental harms as the EPA continues to leave gaps in enforcement.

Suncor marks one of many lawsuits seeking to hold fossil-fuel companies accountable for climate-related costs that the companies’ conduct has left states and local communities to bear. Local governments bear substantial costs associated with climate change, while fossil-fuel producers have historically not been required to pay or compensate for the costs created by fossil fuel-related climate change. These lawsuits seek to hold the companies responsible for the environmental and health harms they cause. The Supreme Court’s decision in Suncor could shape the future of many of these similar cases nationwide.

In many ways, this recent batch of climate change lawsuits echo state tobacco litigation in the 1990s, a comparison Justice Kagan also drew during oral arguments. Those lawsuits recovered billions of dollars from tobacco companies for harms caused by their products. That history helps explain the approach and appeal of climate suits seeking to hold a handful of companies accountable for profiting while leaving the public to bear the enormous costs of climate change.

However, if the Court finds state climate claims preempted, we may be left with a regulatory vacuum — especially as the Trump administration rolls back federal climate protections, and challenges to the EPA’s regulatory authority over greenhouse gases rise. If the Court accepts the fossil fuel companies’ argument that climate change’s national and global reach puts these claims beyond state power, communities could be left without meaningful federal protection or state remedies. 

Again, state tobacco litigation illustrates the broader role state litigation can play in protecting public health when federal action falls short. When tobacco’s public health harms went largely unaddressed by the federal government, state lawsuits helped pressure tobacco companies to accept broad restrictions on advertising and marketing. Whether climate lawsuits can play a similar role is a question the Court may answer in Suncor.

Preemption, however, is not the only question before the Court in Suncor. The Court also opted to address Boulder County’s questions regarding whether the Court had jurisdiction (either by statute or Article III of the Constitution) to even review the Colorado Supreme Court’s interlocutory decision. But only Justices Sotomayor and Jackson seemed interested in pressing that issue at oral argument; most of the Court’s questions instead focused on preemption.

Ultimately, past preemption precedent does not offer a clear prediction of the outcome. On Sept. 28, Justice Alito, who faced pressure to step aside because he owns stock in two oil companies, recused himself. This leaves eight justices to decide on an issue that will impact state public health and environmental protection authorities’ ability to address the harms and protect their residents from the rising costs of climate change. 

During oral arguments, the justices sent mixed signals on their approach to the merits of the case, but several justices sought to better define the limits of Boulder’s theory of liability and how far liability lawsuits could extend if the Court agreed with their position. A ruling for the fossil-fuel companies here could leave states with fewer tools to address climate change’s public and environmental health harms, while federal protections continue to recede.