The end of Chevron deference doesn’t remove the EPA’s authority to enforce emissions laws, especially those established under the Clean Air Act. Courts may now review agency actions more critically, but the Clean Air Act still stands, and so do the regulations that prohibit tampering with emissions systems.

Here’s what the ruling changes—and what it doesn’t:

• More scrutiny on new regulations: Courts will now closely examine the EPA’s future interpretations of environmental laws. New regulations could face longer legal battles, delaying their implementation. However, this scrutiny will apply to future rules, not current emissions standards.
• Existing emissions laws remain unchanged: The Clean Air Act still prohibits emissions tampering, including removing or disabling components like Diesel Particulate Filters (DPFs), Selective Catalytic Reduction (SCR) systems, and catalytic converters. The Chevron decision does not alter these laws.
• EPA enforcement continues: The EPA and state agencies like California’s Air Resources Board (CARB) will continue enforcing emissions standards and issuing penalties for violations. Deleting your truck’s emissions system still carries significant legal and financial consequences, including hefty fines.

The Clean Air Act makes it illegal to tamper with, remove, or defeat any emissions control device installed on your truck. This includes DPFs, SCR systems, and other components designed to reduce emissions. These systems are in place to limit the amount of harmful pollutants, like particulate matter (PM) and nitrogen oxides (NOx), released into the air.

Deleting your truck’s emissions system—sometimes referred to as “rolling coal”—not only increases pollution but also violates federal law. The penalties for tampering with emissions controls are severe:

1. EPA fines: Fines for violating emissions laws can reach up to $4,819 per violation for individuals. For businesses, the fines can be as high as $48,192 per violation. Each tampered vehicle is considered a separate violation, which means the total penalties can add up quickly.
2. State penalties: Some states, especially California, have even stricter emissions standards than federal requirements. CARB aggressively enforces emissions laws and has issued substantial fines to companies that sell or use defeat devices. For example, Sinister Diesel was fined $1 million for selling defeat devices that allowed trucks to bypass emissions controls.
3. Emissions testing: Many states require periodic emissions testing for diesel vehicles. If your truck has had its emissions system deleted, it will likely fail these tests, making it illegal to operate on public roads.
4. Warranty voiding: Deleting emissions systems can void your truck’s manufacturer warranty. This means that any future repairs or issues related to your tampered engine won’t be covered, leaving you to foot the bill for costly fixes.

For nearly four decades, this doctrine provided federal agencies like the Environmental Protection Agency (EPA) significant latitude to interpret and enforce environmental laws, including emissions regulations for diesel engines. This meant that the EPA could interpret broad mandates under laws like the Clean Air Act and implement rules to reduce air pollution, often with support from the courts.

However, in June 2024, the Supreme Court decided to overturn the Chevron Doctrine in the case of Loper Bright Enterprises v. Raimondo. The ruling signaled that courts should no longer automatically defer to agencies like the EPA when interpreting ambiguous statutes. Instead, judges will more closely scrutinize the agency’s interpretation of the law. While this decision will likely influence how future regulations are developed, it does not invalidate existing emissions laws or make emissions tampering legal.

Some truck owners might consider deleting their emissions systems to avoid the costs of maintaining DPFs or to improve performance. However, the potential consequences far outweigh the short-term benefits:

• Costly fines: The penalties for tampering with your truck’s emissions system can be enormous. These fines can apply to each tampered vehicle, adding up quickly, especially for fleet operators.
• Reduced resale value: Trucks with deleted emissions systems often have lower resale values, as potential buyers are aware of the risks involved. Additionally, many states won’t register trucks that have been tampered with, further reducing their value.
• Mechanical issues: Deleting emissions systems can lead to engine performance problems over time. Modern trucks are designed to work with emissions controls in place, and tampering with these systems can lead to mechanical breakdowns, increased fuel consumption, and higher maintenance costs.
• Legal risks: Truck owners and fleet operators who delete emissions systems can face lawsuits and other legal action from both federal and state governments. The legal risks are simply too high to justify tampering with emissions controls.