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September 22, 2022

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EPA Updates Enforcement Policy for Tampering and Defeat Devices

On November 23, 2020, EPA issued a prepublication notice regarding (i) the availability of EPA’s revised enforcement policy for vehicle and engine tampering and aftermarket defeat devices and (ii) EPA’s request for comment on whether and how to update or withdraw EPA’s 1986 catalyst policy.

Key Takeaways

  • EPA’s revised tampering and defeat devices enforcement policy reaffirms EPA’s current practice of exercising enforcement discretion where a person “has a documented, reasonable basis to conclude that the conduct does not adversely affect emissions.” The revised policy provides six examples of circumstances that will generally constitute a “reasonable basis.”

  • EPA seeks comment on whether to update or withdraw its 1986 catalyst policy. Parties have 60 days to comment following publication in the Federal Register.

  • These actions are consistent with EPA’s increased enforcement against tampering and defeat devices pursuant to EPA’s 2020-2023 National Compliance Initiatives. They are also consistent with a recent EPA report finding that emissions controls have been removed from over 550,000 diesel pickup trucks during the past decade – approximately 15% of the national population and the emissions equivalent of adding 9 million non-tampered diesel pickup trucks to the road.

Revised Enforcement Policy

Section 203(a)(3) of the Clean Air Act prohibits tampering with emissions controls and also prohibits making or selling products with a principal effect of bypassing, defeating, or rendering inoperative emissions controls.

EPA’s revised enforcement policy reaffirms and continues EPA’s “longstanding practice of using enforcement discretion not to pursue conduct that could potentially constitute a violation of the Clean Air Act if the person engaging in that conduct has a documented, reasonable basis to conclude that the conduct does not adversely affect emissions.”

EPA’s prior enforcement policies pre-date the 1990 amendments to the Clean Air Act that added the defeat device prohibition alongside the tampering prohibition. The revised policy also speaks in terms of today’s technology, which has advanced substantially, and supersedes and replaces three prior documents, most notably EPA’s 1974 Mobile Source Enforcement Memorandum 1A. EPA explains in the prepublication notice that it has updated its enforcement policy in an effort to help aftermarket parts manufacturers, distributors, service technicians, and others avoid violations.

The revised policy includes six examples of how a person may document a “reasonable basis” that their conduct does not adversely affect emissions:

  • Reasonable Basis A: identical to the EPA-certified configuration
  • Reasonable Basis B: replacement after-treatment system that is as effective as the vehicle’s or engine’s original system and is durable enough to last for a period of time equal to at least half of the vehicle’s or engine’s useful life as defined in EPA regulations
  • Reasonable Basis C: addition of a new after-treatment system to decrease emissions
  • Reasonable Basis D: emissions testing demonstrates no adverse effect on emissions
  • Reasonable Basis E: aftermarket part certified or approved by EPA
  • Reasonable Basis F: aftermarket part exempted by the California Air Resources Board (CARB) through the issuance of a CARB executive order (EO)

EPA will typically only consider the documentation of a “reasonable basis” to be relevant if that documentation exists at or before the time the conduct that might be a potential violation occurs. Additionally, where a person relies on emissions testing to document any of the above reasonable bases, the testing and documentation must generally be the same as required by regulation (e.g. 40 C.F.R. Part 1065) for the purposes of original EPA certification of the vehicle, engine, or equipment at issue.

The policy does not address potential tampering and defeat device violations by original equipment manufacturers (OEMs).

Catalyst Policy

EPA’s revised enforcement policy for tampering and defeat devices neither supersedes nor replaces EPA’s 1986 catalyst policy.

The 1986 policy does not require replacement catalysts to be as effective as OEM catalysts so long as the catalysts reduce emissions by a certain percentage for at least 25,000 miles. However, the revised tampering and defeat devices enforcement policy’s Reasonable Basis B now extends the 25,000-mile durability requirement to at least half of the vehicle’s or engine’s useful life (e.g., 60,000 miles for the most common 120,000 miles useful life vehicles).

EPA now requests comment on whether and how to update or withdraw the 1986 catalyst policy. Specifically, EPA seeks information on whether it has accomplished the goals of the 1986 policy; whether it should establish a consistent enforcement policy for all types of replacement after-treatment systems for vehicles and engines; whether and how the 1986 policy affects the market for aftermarket catalysts, the effect of EPA enforcement policy on catalyst costs; and the appropriate timeline for a transition to a new enforcement policy.

Comments on EPA’s catalyst policy are due 60 days following publication of EPA’s notice in the Federal Register.


EPA’s actions are consistent with its stepped up enforcement against tampering and defeat devices in response to what it characterizes as “widespread removal of vehicle emissions controls that are essential for achieving and maintaining the National Ambient Air Quality Standards.” The Trump EPA has elevated defeat device enforcement to EPA’s list of National Compliance Initiatives for 2020-2023.

EPA’s notice also comes on the heels of a November 20, 2020 EPA report finding that emissions controls have been removed from more than 550,000 diesel pickup trucks. EPA reports that these tampered trucks constitute about 15% of the national population of diesel trucks and have resulted in an air quality impact equivalent to adding more than 9 million non-tampered diesel pickup trucks to the road.

Regulated entities should expect tampering and defeat device enforcement to remain a priority for the Biden EPA because such enforcement has had bipartisan support. In light of EPA’s position that it will typically only consider documentation of a “reasonable basis” created at or before the time a potential violation occurs, companies should carefully evaluate whether they are collecting all necessary information to substantiate their reasonable bases to help facilitate a favorable resolution when faced with EPA’s exercise of enforcement discretion.

© 2022 Beveridge & Diamond PC National Law Review, Volume X, Number 343

About this Author

Daniel B. Schulson Environmental & Administrative Attorney Beveridge & Diamond Washington, DC

Daniel Schulson applies the insight and experience he gained from working in the Office of General Counsel at the U.S. Environmental Protection Agency to clients’ challenges on a broad array of issues.

He assists clients with many aspects of environmental and administrative law, including compliance counseling, permitting, due diligence, audits, commenting on agency rulemakings, administrative enforcement defense, and litigation.

Examples of Dan’s experience include:

  • Providing counsel to the U.S. government-appointed Independent...
Joshua H. Van Eaton Environmental Litigation Attorney Beveridge & Diamond Washington, DC

Joshua H. Van Eaton helps clients resolve high-stakes compliance, enforcement, and litigation matters.

He brings the perspective gained from a distinguished U.S. government service career to provide clients with strategic counsel on air, water, and waste issues with a focus on mobile source emissions. He also litigates those matters and advises on proactive environmental compliance strategies.

Prior to joining Beveridge & Diamond, Josh served as Senior Trial Attorney in the Environmental Enforcement Section of the Environment and Natural Resources Division (ENRD) of the U...

Dylan J. King Environmental Litigation Attorney Beveridge & Diamond Boston, MA

Dylan uses his legal and business skills to help clients solve problems.

He maintains a diverse environmental litigation and regulatory practice, working with clients nationwide across industrial sectors. He has developed experience with solid waste facility siting, pipeline and hazardous material transportation regulations, site contamination litigation, and local zoning matters. Dylan joined the firm following his graduation from Vermont Law School with a certificate in Energy Law.

During his time at Vermont Law School, Dylan worked with the Vermont Law School Energy Clinic...