Sabin Center Files Amicus Brief Amid Trump Transition to Support EPA’s Heavy-Duty Vehicle Standards  – Climate Law Blog

Yesterday, January 21, 2025, the Sabin Center filed an amicus brief on behalf of the National League of Cities (NLC) and the U.S. Conference of Mayors (USCM) in support of the U.S. Environmental Protection Agency’s (EPA) 2024 greenhouse gas emissions standards for heavy-duty vehicles (the “HDV Rule”) that went into effect on June 21, 2024. Our involvement in this case, Nebraska v. EPA, represents the Center’s most recent effort to support strong federal climate regulations that protect and advance the wellbeing of cities and their residents. In the last four months, the Sabin Center has submitted four amicus briefs supporting EPA’s 2024 rulemakings, including briefs in West Virginia v. EPA (concerning power plant emissions standards) and Kentucky v. EPA (concerning light- and medium-duty vehicle emission standards), that bring the unique perspective of cities and other local governments before the courts. 

In Nebraska v. EPA, 24 states and industry groups challenged the HDV Rule, which revises the greenhouse gas emission standards for heavy-duty vehicles, model year 2027, and sets new standards to lower greenhouse gas emissions from model years 2028-2032. Plaintiffs argued that EPA exceeded its authority in promulgating the rules, including by establishing fleetwide average standards that would likely result in the production and sale of more electric vehicles. As in other Sabin Center briefs, we underscore the essential role local governments play in addressing the climate crisis, highlighting their frontline position in mitigating and managing climate impacts. In particular, we discuss the severe adverse effects that heavy-duty vehicles have on local air pollution and public health in cities, and especially in disadvantaged communities. Cities endeavoring to protect those and other residents are constrained in their authority to do so, and by promulgating the HDV Rule, EPA has fulfilled its statutory mandate to set standards that protect and advance the wellbeing of cities and their residents. Of course, at this moment of transition in Washington, the fate of both this litigation and the HDV Rule are vulnerable to shifting priorities as the second Trump administration takes office. 

Amicus Brief on Behalf of National League of Cities and U.S. Conference of Mayors

The Clean Air Act’s opening provision recognizes that vehicles contribute to dangerous air pollution and that federal “leadership is essential for the development of cooperative Federal, State, regional, and local programs to prevent and control air pollution.” 42 U.S.C. § 7401. Because section 209(a) of the Clean Air Act broadly preempts states and local governments from adopting vehicle emissions standards that differ from federal standards, cities rely on federal regulation to support their own climate adaptation and mitigation efforts. 

In our brief filed on behalf of NLC and USCM, we argue that cities rely on robust federal rules to bolster their own efforts to mitigate greenhouse gas emissions and protect against the impacts and costs associated with climate change. This is especially true in the case of heavy-duty vehicles, which have significant negative public health and climate impacts in cities, but whose regulation falls largely outside municipal jurisdiction. Large, diesel powered heavy-duty vehicles make up just 10% of on-road vehicles but produce more than half of particulate matter from on-road vehicles. Because of the increased presence of heavy-duty vehicles and traffic congestion in urban areas, cities and their residents are uniquely harmed by their emissions. The HDV Rule directly addresses the adverse effects of those emissions, and specifically, is a boon to the public health of disadvantaged communities situated near major roadways and industrial hubs. We also argue that the HDV Rule falls well within EPA’s authority to regulate mobile sources and that it is critical to ensuring the cooperative regulatory framework set out by the Clean Air Act.

More broadly, the Sabin Center’s brief describes how cities of all sizes and in every region of the country are disproportionately harmed by the increasingly severe impacts of climate change, and that they must also foot the bill for its ever-rising costs. From more frequent and severe hurricanes, to intense heat waves and unprecedented droughts, the health and well-being of cities and their residents are threatened by climate impacts that cost cities billions of dollars each year. 

We also explore the ways in which cities of all sizes lead the response to climate change through mitigation measures that reduce greenhouse gas emissions from the transportation sector and creative adaptation solutions that protect residents from urban heat impacts and future extreme weather events. Hundreds of cities, large and small, have set ambitious greenhouse gas reduction goals and crafted climate action plans that set forth actionable, equitable decarbonization pathways for their communities. Local governments’ transportation sector mitigation efforts include electrifying their fleets, installing electric vehicle charging infrastructure, requiring or incentivizing that electric vehicle infrastructure be installed through building codes or local laws, and investing in alternative forms of transportation. 

How the Second Trump Administration May Affect the HDV Rule

While the HDV Rule addresses urgent local health and climate concerns, it faces an uncertain future due to the stark shift in federal priorities under the second Trump administration. The new administration has signaled its intent to rollback critical environmental protections, which could leave urban communities vulnerable to continued pollution from heavy-duty vehicles. Such a shift would not only undermine the progress made by the EPA but could also entrench harmful emissions that disproportionately affect cities and their residents for years to come.

On Day 1, President Trump signed an Executive Order titled “Unleashing American Energy” declaring, among other things, that agencies must review “all actions that potentially burden the development of energy resources” in the United States including, it would seem, actions that relate to a falsely claimed “electric vehicle (EV) mandate[.]” After reviewing relevant actions, agencies are directed to notify the Attorney General of “any steps taken[,]” which may include an intention to repeal a final, effective rule, so that the Attorney General can “(i) provide notice of this Executive Order and any such actions to any court with jurisdiction over pending litigation in which such actions may be relevant; and (ii) request that such court stay or otherwise delay further litigation. . .” The EPA under the second Trump administration is likely to seek a stay in the litigation while it reviews the rule, possibly referring to the provisions of the Executive Order in doing so. If a stay is sought and granted here, enforcement of the HDV rule would be delayed, leaving cities and their residents vulnerable to the ongoing health, climate, and economic impacts of heavy-duty vehicle emissions.

In addition to seeking a stay, EPA is also likely to initiate a repeal of the HDV Rule at some point in the future. In doing so, EPA would be required to adhere to the Administrative Procedure Act requirements for any rule modifications, which generally requires a new rulemaking with opportunities for public comment. Further, it would be required to provide a replacement rule with as laborious a justification as the rule it seeks to modify or reverse. 

The second Trump administration’s likely repeal and replacement of the HDV Rule will face major legal opposition and judicial scrutiny. The process will also likely take years, during which time the Sabin Center will continue to support local governments advocating for federal climate rules that protect the health and wellbeing of their residents.

Vincent M. Nolette is the Sabin Center’s Equitable Cities Climate Law Fellow.