CAA section 113, found within Subchapter I, provides for criminal penalties for violations of certain prohibitions or requirements of the Act. One such criminal violation is knowingly tampering with any required “monitoring device or method,” which carries a potential two-year prison term. CAA section 202, found within Subchapter II, requires the installation of on-board diagnostic (OBD) systems in motor vehicles. These systems monitor virtually every component that can affect emission performance and alert the vehicle operator to malfunctions by illuminating the vehicle’s “check engine” light. Installing a so-called “defeat device” is often accompanied by tampering with these OBD systems so as to prevent them from recognizing that the vehicle or engine is functioning differently than originally designed and certified. In such situations, EPA has begun pursuing criminal penalties for installing aftermarket defeat devices, alleging that defendants have violated the Clean Air Act’s antitampering provision by tampering with a vehicle’s OBD system during the installation.
Arguments for and against EPA’s interpretation of section 113
EPA has asserted in court filings that the expansive language of the tampering provision simply means what it says: that it applies to “any” monitoring device required under any provision of the CAA, including OBD systems required by section 202 of the Act. (United States v. Jonathan Long No. 2:22-CR-00139 (E.D. Va. 2024). By contrast, defendants in these enforcement cases rely primarily on a structural argument claiming that because the criminal penalty provisions exist only in Subchapter I, criminal enforcement is limited to violations of the stationary source provisions found in that subchapter. This is buttressed by the fact that Subchapter II creates distinct civil penalties for this same conduct––the $2,500 fine. In the case of Jonathan Long, EPA ultimately prevailed, with Mr. Long pleading guilty to one count and currently set for sentencing in late April 2025.
Defendants further argue that OBD systems are not “monitoring devices” within the CAA’s meaning because they do not measure actual emissions, nor do they produce data or records that can be used to ensure compliance with the Act. EPA responds by referencing the ordinary meaning of the phrase, arguing that OBD systems fall squarely within the dictionary definition of “monitoring device.”
Federal district court opinions on the issue
In 2024, three federal district courts, in Washington, Missouri, and Virginia, took up this question of whether OBD tampering could be criminalized under section 113. Relying heavily on reasoning based on a textualist approach, all three courts answered in the affirmative. In the first of the three cases, United States v. Coiteux, the Western District of Washington determined that criminal sanctions facially apply to any person who tampers with any monitoring device required under the entire CAA, not merely Subchapter I. The court further concluded that OBD systems are monitoring devices for the purposes of the tampering provision, relying on the plain and ordinary meaning of those terms. In doing so, Judge Settle criticized the defendant’s argument, saying that she failed to “explain how an OBD could diagnose a problem with the emissions system without monitoring that system.” A jury subsequently convicted Coiteux on all counts. The defendants have filed an appeal with the U.S. Court of Appeals for the Ninth Circuit, U.S. v. Coiteux, No. 24-6945 (appeal docketed Nov. 15, 2024).
The Eastern District of Missouri adopted the Coiteux court’s reasoning in a ruling on a motion in limine in United States v. Carroll. The defendants in that case claimed that, because the Clean Air Act uses the phrases “diagnostic systems” and “monitoring devices” in different places, Congress envisioned a difference in meaning. The court was not convinced, once again relying on the plain meaning of the phrase—monitoring device. In August 2024 a jury found defendant Christopher Lee Carroll, who allegedly used defeat devices guilty of device tampering. In February 2025 the Court sentenced Carroll to nine years in prison and to pay $3 million in restitution.
The Eastern District of Virginia addressed the plain language argument directly in United States v. Long . Judge Gibney quoted the Supreme Court in saying that “[i]n statutory interpretation disputes, a court’s proper starting point lies in a careful examination of the ordinary meaning and structure of the law itself.” “Where[] . . . that examination yields a clear answer, judges must stop.” Accordingly, the court once again found that the plain language yielded a clear answer: that the tampering provision applies to monitoring devices required under any part of the Clean CAA, including tampering with OBD systems. Long subsequently pleaded guilty.
Looking ahead
The Coiteux decision has since been appealed to the Ninth Circuit, so it remains to be seen whether the Court of Appeals will agree with the District Court’s plain language reading of the statute. One can anticipate that they will. There has been a judicial trend toward textualist statutory interpretation at the Supreme Court level in the past several decades, and that trend has trickled down into the Courts of Appeals. As Justice Gorsuch said in 2020, “[o]nly the written word is the law[.]” Accordingly, that sentiment is likely to prevail as these OBD tampering cases continue to be litigated. However, with the Trump administration launching aggressive rollbacks of pollution prevention and climate change–related rules, it remains unclear as to whether the new EPA will continue to prioritize combatting defeat devices on vehicles and will utilize this prosecution strategy in doing so.
