The Post-Chevron Vulnerability Matrix: Agency Action After Loper Bright

Mapping the structural exposure of agency action after the restoration of independent judicial judgment under 5 U.S.C. § 706

LAW Research Division · LAW Research 3(1) · 2026

Abstract

The Supreme Court's overruling of Chevron U.S.A. Inc. v. Natural Resources Defense Council, Inc., 467 U.S. 837 (1984), in Loper Bright Enterprises v. Raimondo, 144 S. Ct. 2244 (2024), exposes a structural vulnerability spanning forty years of agency action. Under Chevron Step Two, courts deferred to an agency's "permissible" or "reasonable" interpretation of an ambiguous statute. Loper Bright restored the constitutional baseline: under 5 U.S.C. § 706, reviewing courts "shall decide all relevant questions of law" and "interpret constitutional and statutory provisions" — a duty that cannot be delegated. This paper maps the vulnerability matrix across five categories of agency action — regulations, guidance documents, adjudications, pre-Chevron rules, and state administrative law — and identifies the procedural mechanisms through which each category may be challenged. The notice-and-comment record becomes the critical litigation resource: the agency must now prove that its interpretation is correct, not merely that it was reasonable. The analysis demonstrates that the restoration of independent judicial judgment under § 706 is not an innovation but a return to the constitutional baseline established in Marbury v. Madison, 5 U.S. 137 (1803): "It is emphatically the province and duty of the judicial department to say what the law is." A litigation strategy template is provided for structuring post-Loper Bright challenges, organized around front-loading statutory interpretation, exploiting the notice-and-comment record, mapping vulnerability by category, and preserving state-law arguments.

I. Introduction

For forty years, Chevron deference structured the relationship between federal courts and administrative agencies. The framework was deceptively simple. Under Step One, a court asked whether Congress had "directly spoken to the precise question at issue." If the statute was unambiguous — if Congress's intent could be discerned through the traditional tools of statutory construction — the inquiry ended, and the statute controlled. Under Step Two, if the statute was "silent or ambiguous with respect to the specific issue," the court deferred to the agency's interpretation so long as it was "based on a permissible construction of the statute." Chevron, 467 U.S. at 842–43.

Chevron deference migrated from a tool of statutory interpretation to a structural principle of administrative governance. Agencies relied on it when promulgating regulations, issuing guidance, adjudicating enforcement actions, defending their interpretations in litigation, and structuring their internal decision-making processes. The doctrine's breadth meant that courts rarely exercised independent judgment on questions of statutory interpretation arising in agency contexts. The agency's interpretation was the de facto law, subject only to the outer boundary of impermissibility — a boundary that, in practice, was almost never crossed. Between 1984 and 2024, Chevron was cited in thousands of federal court decisions, and Step Two became the default mode of judicial review for agency statutory interpretation.

The consequences were structural. Agencies could change interpretations with changes in administration without congressional authorization, knowing that each interpretation would receive Chevron deference so long as it was "reasonable." The regulated community could not rely on the stability of statutory meaning; the same statute could mean one thing under one administration and another under the next, with both interpretations entitled to judicial deference. Congress, knowing that agencies — not courts — would resolve statutory ambiguities, drafted statutes with deliberate ambiguity, delegating policy choices to agencies without the political accountability that clear statutory commands require.

Loper Bright ended this regime. Writing for the majority, Chief Justice Roberts grounded the holding in the text of the APA itself: "The APA requires courts to 'decide all relevant questions of law' and 'interpret constitutional and statutory provisions.' It does not require courts to defer to an agency's interpretation of the law simply because a statute is ambiguous." 144 S. Ct. at 2263. The Court did not overrule the cases that Chevron had governed — it overruled the deference framework itself. Every regulation, guidance document, and adjudication upheld under Chevron Step Two is now subject to challenge on the ground that the agency's interpretation, while "permissible" under the old standard, was not "correct" under independent judicial judgment.

This paper maps the vulnerability matrix across five categories of agency action and identifies the procedural mechanisms through which each category may be challenged. Part II analyzes each category in detail, assessing vulnerability ratings and identifying the doctrinal hooks most likely to succeed in post-Loper Bright litigation. Part III examines the Marbury baseline that Loper Bright restores. Part IV provides a litigation strategy template for firms challenging agency action in the post-Chevron landscape. Part V assesses the systemic implications for administrative governance.

II. The Vulnerability Matrix

The vulnerability matrix maps five categories of agency action according to their structural exposure to post-Chevron challenge. Each category is assessed for (a) the procedural mechanism available for challenge, (b) the statute of limitations applicable, (c) the strength of the legal argument under Loper Bright, and (d) the practical barriers to successful challenge.

A. Category I: Regulations Upheld Under Chevron Step Two

Regulations that survived judicial review solely because the agency's interpretation was "reasonable" — rather than "correct" — constitute the most exposed category. The procedural mechanism for challenge is a direct action under the APA, 5 U.S.C. § 702, seeking vacatur on the ground that the regulation rests on a statutory interpretation that a reviewing court, exercising independent judgment, would reject.

The six-year statute of limitations under 28 U.S.C. § 2401(a) bars facial challenges to regulations promulgated more than six years before filing. This temporal limitation is significant: regulations promulgated before 2020 (approximately 2018 at the time of this writing) may be facially immune from direct challenge under the APA's statute of limitations. However, three doctrines mitigate this temporal bar.

First, regulations applied in enforcement actions are subject to as-applied challenge at any time. An agency that brings an enforcement action based on a regulation upheld under Chevron Step Two must now defend the underlying statutory interpretation on correctness grounds, not mere reasonableness. The as-applied challenge route is available even for regulations decades old, so long as the agency continues to enforce them.

Second, the "reopening" doctrine permits challenge when an agency reexamines or reaffirms a rule. If an agency issues a notice of proposed rulemaking that reopens the underlying statutory question — or denies a petition for rulemaking with a substantive defense of the existing interpretation — the statute of limitations resets. This doctrine, developed in NRDC v. EPA, 571 F.3d 1245 (D.C. Cir. 2009), and CTIA-Wireless Association v. FCC, 466 F.3d 105 (D.C. Cir. 2006), has particular significance post-Loper Bright: any agency action that substantively reaffirms a pre-2020 regulation may open the door to a facial challenge regardless of the original promulgation date.

Third, under Loper Bright itself, the Court clarified that statutory stare decisis does not protect Chevron-deferential precedents in the same way that it protects interpretations reached through independent judicial judgment. A prior decision that deferred to an agency's "reasonable" interpretation under Step Two did not independently determine the statute's meaning; it merely ratified the agency's determination. Such decisions are entitled to less precedential weight than decisions in which the court itself determined the correct interpretation. Vulnerability rating: HIGH.

B. Category II: Guidance Documents and Sub-Regulatory Pronouncements

Agency guidance documents, interpretive rules, and policy statements that rely on Chevron-derived interpretations are vulnerable under Loper Bright in two distinct respects.

First, to the extent these documents assert legal interpretations without having undergone notice-and-comment rulemaking, they are independently vulnerable under the APA's procedural requirements. Under Appalachian Power Co. v. EPA, 208 F.3d 1015 (D.C. Cir. 2000), a guidance document that "imposes binding obligations" on regulated parties is a legislative rule requiring notice and comment, regardless of the agency's characterization. Loper Bright strengthens this argument: an agency cannot evade judicial review of its statutory interpretations by embedding them in guidance documents that are procedurally exempt from pre-enforcement challenge, while simultaneously claiming Chevron deference for those interpretations when they are challenged.

Second, under Loper Bright, courts reviewing guidance documents no longer defer to the agency's underlying statutory interpretation. The notice-and-comment record — the contemporaneous documentation of the agency's interpretive reasoning at the time of promulgation — becomes the critical litigation resource: the agency must prove that its interpretation is correct, not merely that it was reasonable. For guidance documents, which often lack the detailed interpretive record that accompanies notice-and-comment rulemaking, this burden is particularly difficult to meet.

The practical exposure in this category is amplified by the independent vulnerability of guidance documents on procedural grounds. A litigant challenging a guidance document can argue both that the agency's interpretation is incorrect (under Loper Bright) and that the document itself exceeds the agency's authority or was promulgated without required procedures (under the APA). These arguments are complementary: the agency cannot claim that its interpretation is entitled to deference because it was arrived at through a process that lacks the procedural safeguards that might otherwise warrant judicial respect. Vulnerability rating: HIGH.

C. Category III: Agency Adjudications

Agency adjudications that applied Chevron-deferential interpretations are vulnerable on direct appeal. Under Loper Bright, the reviewing court applies independent judgment to the agency's statutory interpretation. The practical exposure includes:

(a) Pending appeals. Any appeal from an agency adjudication in which the agency invoked Chevron deference at the agency level is now governed by Loper Bright. The reviewing court must determine the correct interpretation of the statute, not merely assess whether the agency's interpretation was reasonable.

(b) Final adjudications subject to collateral attack. Where the agency's statutory interpretation was outcome-determinative, a party may seek relief from the final order under the APA or the agency's organic statute on the ground that the interpretation was erroneous. The availability of collateral relief depends on the specific statutory scheme, the finality of the order, and the availability of direct review.

(c) Inseparable fact-law determinations. In adjudications where the agency's factual findings are inseparable from its legal interpretation — for example, where the agency applied a Chevron-deferential interpretation to find that certain conduct violated an ambiguous statutory provision — the entire determination may be unstable. If the legal interpretation on which the factual finding depends is incorrect under independent judicial review, the factual finding may not survive. Vulnerability rating: MODERATE-HIGH.

D. Category IV: Pre-Chevron Agency Rules

Regulations and interpretations predating Chevron (1984) that were subsequently defended under Chevron principles present a complex analytical question. A rule promulgated under the pre-Chevron standard would not have relied on Chevron deference for its initial validity, because Chevron had not yet been decided. The agency's interpretation at the time of promulgation was presumably the agency's independent judgment about the statute's meaning — an interpretation that would be assessed under the Skidmore standard applicable before Chevron. Skidmore v. Swift & Co., 323 U.S. 134 (1944).

However, if the rule's survival in subsequent litigation depended on Chevron Step Two — that is, if a court upheld the rule against a post-1984 challenge on the ground that the agency's interpretation was "reasonable" rather than "correct" — the post-Loper Bright vulnerability attaches at the point of that subsequent reliance. The rule's initial validity is not in question, but its continued validity may be, if a court exercising independent judgment would reject the interpretation on which the rule depends.

Pre-1984 rules that have not been relitigated in the intervening decades may be the most stable category — not because they are immune from challenge, but because the passage of time and the statute of limitations reduce their exposure to direct facial attack. However, this stability is relative, not absolute: a pre-1984 rule enforced in an as-applied proceeding may be challenged on the ground that the interpretation underlying it is incorrect, regardless of the rule's age. Vulnerability rating: MODERATE.

E. Category V: State Administrative Law

Loper Bright directly governs federal-court review of federal agency action. It does not, by its terms, overrule state-level Chevron analogues. However, state supreme courts that adopted Chevron-style deference as a matter of state administrative law — often citing Chevron itself — must now decide whether to follow Loper Bright as a matter of state jurisprudence.

The exposure in this category is structural rather than directly precedential. Loper Bright provides the reasoning, but state supreme courts must apply it. State administrative regulations upheld under Chevron-analogue deference are vulnerable where state courts adopt Loper Bright's reasoning as a matter of state administrative law.

The analysis varies significantly by jurisdiction. Approximately 35 states have adopted some form of Chevron-style deference to agency statutory interpretations. Some have done so by judicial decision citing Chevron; others have codified the standard in state administrative procedure acts. In states where the deference doctrine is judge-made, state supreme courts may revisit it in light of Loper Bright without legislative action. In states where the deference doctrine is codified, legislative amendment may be required — though state courts may interpret the statute narrowly in light of Loper Bright's reasoning.

The jurisdictional variance in this category is substantial. States with strong independent judicial traditions — including Michigan, whose constitution vests the judicial power in "one court of justice" and whose supreme court has asserted independent interpretive authority — are more likely to follow Loper Bright than states whose administrative law doctrine is built on federal Chevron precedent. Vulnerability rating: VARIABLE BY JURISDICTION.

III. The Marbury Baseline

Loper Bright restores the constitutional architecture that Marbury v. Madison established in 1803. Chief Justice Marshall's formulation — "It is emphatically the province and duty of the judicial department to say what the law is" — recognizes that statutory interpretation is a judicial function. The APA codifies this principle at § 706: "The reviewing court shall decide all relevant questions of law, interpret constitutional and statutory provisions, and determine the meaning or applicability of the terms of an agency action."

Chevron created an exception to this principle for ambiguous statutes. Under Step Two, the court did not "say what the law is" — it deferred to the agency's statement of what the law is, so long as the agency's statement was reasonable. The court's role was reduced from interpreter to reasonableness reviewer. The agency, not the court, was the primary interpreter of the statutes it administered.

Loper Bright closes this exception. The restoration of the Marbury baseline has consequences beyond the specific categories of agency action discussed above. It restores to courts the power — and the duty — to decide independently whether an agency's interpretation of the statutes it administers is correct. Under Chevron, the agency was the primary interpreter and the court was a reasonableness reviewer. Under Loper Bright, the court is again the primary interpreter. The agency's views may be persuasive — they may even be correct — but they are not entitled to deference simply because they are the agency's.

This restoration has implications for judicial methodology. Under Chevron, a court's analysis was structured as a two-step inquiry: first, determine whether the statute was ambiguous; second, if so, determine whether the agency's interpretation was reasonable. The court's independent judgment about the statute's meaning was relevant only at Step One. Under Loper Bright, the court's independent judgment is relevant from the outset. The court must determine the statute's meaning using the traditional tools of statutory construction — text, structure, history, purpose — without the filter of agency deference.

The restoration also has implications for the separation of powers. Under Chevron, agencies exercised what was effectively a law-interpreting function — a function the Constitution assigns to the judiciary. Loper Bright returns that function to the courts. The return is structural, not policy-driven: it does not matter whether agency interpretation is "better" or "worse" than judicial interpretation. The question is which branch the Constitution assigns to perform the function. The Court in Loper Bright answered that question by reference to the text of § 706 and the constitutional structure of judicial review.

IV. Litigation Strategy Post-Loper Bright

Firms litigating against agency action should restructure their briefing around the Loper Bright framework. The following template provides a structured approach to post-Chevron challenges.

1. Front-Load Statutory Interpretation

Under Chevron, a challenger had to clear Step One before reaching Step Two — a burden that required the challenger to demonstrate that the statute was unambiguous and that the agency's interpretation contradicted it. Under Loper Bright, the court exercises independent judgment from the outset. The challenger is no longer required to prove that the statute is unambiguous; it is sufficient to prove that the agency's interpretation is incorrect.

This shift has practical implications for briefing structure. Under Chevron, a brief would typically argue (a) that the statute was unambiguous, and (b) in the alternative, that the agency's interpretation was unreasonable. Under Loper Bright, the brief should argue that the agency's interpretation is incorrect, using the full range of statutory construction tools: text, structure, history, purpose, and precedent. The alternative argument that the interpretation is unreasonable — which was the primary argument under Step Two — is no longer necessary, though it may be preserved for completeness.

2. Exploit the Notice-and-Comment Record

The agency's contemporaneous interpretive reasoning is the primary target. If the record reflects ambiguity or reliance on policy preference rather than textual analysis, the agency's interpretation is vulnerable to an argument that it is not the "best" reading of the statute. The notice-and-comment record should be mined for:

• Admissions that the statute is ambiguous (an admission that, under Loper Bright, invites the court to resolve the ambiguity rather than defer to the agency's resolution)
• Policy justifications that are untethered to statutory text (evidence that the agency's interpretation is based on policy preference rather than statutory meaning)
• Contemporaneous alternative interpretations considered and rejected by the agency (evidence that the agency's chosen interpretation was not compelled by the text)
• Changes in interpretation across administrations (evidence that the agency's interpretation is not a consistent reading of the statute but a policy choice)

3. Map the Vulnerability Matrix

Not all agency action is equally exposed. Category I (regulations upheld under Step Two) and Category II (guidance documents) present the highest-probability targets. Category III (adjudications) depends on procedural posture. Category IV (pre-1984 rules) requires more careful analysis. Litigation resources should be allocated according to vulnerability, with the highest-confidence challenges pursued first to establish favorable precedent.

4. Preserve State-Law Challenges

In jurisdictions that have adopted Chevron-analogue deference, preserve the argument under Loper Bright for state supreme court review. The state administrative law challenge should be briefed with reference to Loper Bright's reasoning, the state constitution's separation-of-powers provisions, and the state APA's judicial review provisions. Even if the trial court is bound by existing state precedent adopting Chevron deference, the argument must be preserved for appellate review.

V. Systemic Implications

The post-Loper Bright litigation landscape will be shaped by three systemic implications.

First, the volume of challenges to agency statutory interpretations will increase. Every regulation, guidance document, and adjudication upheld under Chevron Step Two is a potential target. The APA's six-year statute of limitations will channel challenges toward recent regulations and as-applied challenges to older regulations, creating a litigation wave concentrated in Categories I and II.

Second, agency behavior will change. Knowing that their statutory interpretations will be reviewed de novo rather than under Chevron deference, agencies will invest more in the textual and structural analysis supporting their interpretations. The notice-and-comment record will become more detailed, with agencies marshaling the full range of statutory construction tools to support their interpretations. The days of agencies claiming deference for skeletal interpretive analyses are over.

Third, congressional behavior may change. Under Chevron, Congress could draft ambiguous statutes knowing that agencies — not courts — would resolve the ambiguities, and that agencies' resolutions would receive judicial deference. Under Loper Bright, Congress knows that courts will resolve statutory ambiguities independently. This may incentivize more precise statutory drafting — or, alternatively, more explicit delegation of interpretive authority to agencies through statutory language that clearly assigns the interpretive function.

VI. Conclusion

Loper Bright is not a change in the law — it is the restoration of the law. The forty-year Chevron experiment ended because the Court recognized that deference to agency legal interpretations is incompatible with the text of the APA and the constitutional structure of judicial review. The vulnerability matrix identifies where that experiment left the most exposure: regulations, guidance documents, and adjudications upheld under a deference framework that no longer exists.

The litigation wave that follows will determine not whether Chevron is dead, but how thoroughly its architecture must be dismantled. The notice-and-comment record — the contemporaneous documentation of agency interpretive reasoning — is now the critical litigation resource. Agencies that relied on Chevron to defend interpretations that were "reasonable" but not "correct" face the prospect of having those interpretations vacated under independent judicial review.

The restoration of the Marbury baseline — courts, not agencies, say what the law is — is not merely a doctrinal correction. It is a structural realignment of the relationship between the judiciary and the administrative state. The forty-year interregnum during which agencies were the primary interpreters of the statutes they administer is over. The courts have resumed their constitutional function.

References

1. Loper Bright Enterprises v. Raimondo, 144 S. Ct. 2244 (2024). Available: https://www.supremecourt.gov/opinions/23pdf/22-451_7m58.pdf

2. Chevron U.S.A. Inc. v. Natural Resources Defense Council, Inc., 467 U.S. 837 (1984). Available: https://supreme.justia.com/cases/federal/us/467/837/

3. Marbury v. Madison, 5 U.S. 137 (1803). Available: https://supreme.justia.com/cases/federal/us/5/137/

4. 5 U.S.C. § 706 — Scope of review. Available: https://www.law.cornell.edu/uscode/text/5/706

5. 5 U.S.C. § 702 — Right of review. Available: https://www.law.cornell.edu/uscode/text/5/702

6. 28 U.S.C. § 2401(a) — Time for commencing action against United States. Available: https://www.law.cornell.edu/uscode/text/28/2401

7. Skidmore v. Swift & Co., 323 U.S. 134 (1944). Available: https://supreme.justia.com/cases/federal/us/323/134/

8. NRDC v. EPA, 571 F.3d 1245 (D.C. Cir. 2009). Available: https://www.cadc.uscourts.gov/

9. CTIA-Wireless Association v. FCC, 466 F.3d 105 (D.C. Cir. 2006). Available: https://www.cadc.uscourts.gov/

10. Appalachian Power Co. v. EPA, 208 F.3d 1015 (D.C. Cir. 2000). Available: https://www.cadc.uscourts.gov/

11. Administrative Procedure Act, Pub. L. 79-404, 60 Stat. 237 (1946).

12. Michigan Constitution, Article VI, § 1. Available: http://legislature.mi.gov/doc.aspx?mcl-article-vi-1

13. United States v. Mead Corp., 533 U.S. 218 (2001). Available: https://supreme.justia.com/cases/federal/us/533/218/

14. Michigan v. EPA, 576 U.S. 743 (2015). Available: https://supreme.justia.com/cases/federal/us/576/743/

Citation

LAW Research Division. (2026). The Post-Chevron Vulnerability Matrix: Agency Action After Loper Bright. LAW Research, 3(1), 1–18.

Distribution

Published: LAW Research, LAW Research 3(1) Status: published