In Loper Bright Enterprises v. Raimondo, 144 S.Ct. 2244 (2024), the Supreme Court overruled Chevron U.S.A., Inc. v. Natural Resources Defense Council and held that courts must exercise their own independent judgment when determining whether an agency has acted within its statutory authority. Courts are no longer required to defer to an agency's interpretation of an ambiguous statute it administers. The decision is primarily an administrative law ruling, but its downstream effects on PI litigation have become clearer over the past two years as defendants in auto, trucking, pharmaceutical, and medical device cases have invoked Loper Bright to challenge the regulatory standards that plaintiffs offer as evidence of the standard of care or as negligence per se predicates.
How Regulatory Standards Function as PI Evidence
Federal safety regulations promulgated by NHTSA, FMCSA, the FDA, and similar agencies have historically served two functions in PI litigation. First, violation of a safety regulation can establish negligence per se if the regulation was designed to protect against the type of harm that occurred and the plaintiff is within the class of persons intended to be protected. Second, compliance with or deviation from a safety regulation is evidence of the standard of care, even where the regulation does not directly apply.
Both functions depend on the underlying regulatory standard being lawfully promulgated and applied. If a court holds that a particular agency interpretation of a statute was outside the agency's authority, the regulation itself may be invalidated or narrowed, removing the regulatory predicate from the negligence per se claim or changing the standard-of-care baseline.
Trucking: FMCSA Hours-of-Service Challenges
Post-Loper Bright, defense carriers in trucking cases have raised challenges to specific FMCSA rules on the ground that the agency exceeded its statutory authority under 49 U.S.C. § 31136. The Ninth and Fifth Circuits have handled initial challenges to FMCSA's 2020 Hours-of-Service final rule amendments, with courts applying the Loper Bright framework to review whether the specific interpretive choices made by FMCSA in expanding the short-haul exception or revising the adverse driving conditions exception were within the agency's authority. As of 2026, no court has invalidated the core hours-of-service framework, but the argument has been preserved by carriers in several pending trucking cases.
Plaintiff counsel in trucking cases should anticipate this challenge and have a response prepared: the core HOS limits (11-hour driving limit, 14-hour window, 60/70-hour weekly caps) are straightforwardly within FMCSA's statutory authority under the Motor Carrier Act Safety provisions and are unlikely to fall. The more vulnerable targets are interpretive rules or guidance documents that stretch beyond the statutory text, such as certain personal conveyance designations or specific electronic logging interpretations that FMCSA has issued as guidance rather than final rule.
Medical Devices: FDA 510(k) Clearance and the Parallel Claim
In medical device product liability cases, Riegel v. Medtronic (2008) established that state law claims that conflict with premarket approval (PMA) requirements are preempted. The narrow escape valve is the parallel claim: a state tort claim that imposes requirements identical to, rather than different from or in addition to, the federal requirements survives preemption. Post-Loper Bright, some defendants have argued that courts should apply more searching scrutiny to FDA's interpretation of what conduct its regulations actually require, potentially narrowing the scope of the “predicate device” comparison that forms the basis of many 510(k) device cases.
Plaintiff counsel pursuing parallel claims in medical device cases should be prepared to address the Loper Bright argument head-on: the parallel claim doctrine turns on the requirements of the federal regulation themselves, not on the agency's interpretation of an ambiguous statute. For most parallel claims, the regulation's text is clear enough that Loper Bright's interpretive deference question does not arise.
NHTSA FMVSS and Auto Product Liability
Federal Motor Vehicle Safety Standards set minimum performance requirements for passenger vehicles. Plaintiff product liability counsel uses NHTSA regulations in crashworthiness, restraint system, and airbag deployment cases. Defendants have occasionally argued that specific FMVSS interpretations adopted by NHTSA are entitled to less deference post-Loper Bright. The stronger plaintiff counter-argument is that FMVSS are promulgated through formal rulemaking after notice and comment, and that even under Loper Bright, a court exercises its own judgment that a comprehensive, notice-and-comment rulemaking represents the best interpretation of the enabling statute.
The Practical Takeaway for PI Practitioners
Loper Bright has not, as of 2026, produced wholesale invalidation of the safety regulations that PI practitioners rely on. But it has opened a new argument in the defense playbook, and plaintiff counsel in regulated-industry cases (trucking, pharma, auto, devices) should anticipate regulatory challenges and brief the continuing validity of the specific standard they rely on. Keep a litigation file on the current status of any federal safety rule that is the centerpiece of your regulatory predicate, and track pending challenges through PACER and the relevant agency's rulemaking docket. For broader coverage of how regulatory changes affect PI case strategy, see the case law and settlements practice section. Trucking regulatory evidence in context appears in the truck and motorcycle practice section.