Regulated Parties May Intervene of Right by Advancing Statutory Arguments the Agency Cannot: Rebutting Adequate-Representation Presumptions in APA Defense of a CWA TMDL

I. Introduction

In Lucas Cnty. Bd. of Comm'rs v. EPA (6th Cir. Mar. 9, 2026), the Sixth Circuit addressed who gets to participate as a party in a high-stakes Administrative Procedure Act (“APA”) challenge to the Environmental Protection Agency’s approval of a Clean Water Act (“CWA”) Total Maximum Daily Load (“TMDL”) for phosphorus in the Maumee River watershed—an issue tied to harmful algal blooms in Lake Erie’s western basin.

The underlying merits dispute (not decided on appeal) is whether U.S. EPA’s approval of Ohio EPA’s 2023 “Maumee TMDL” was arbitrary, capricious, or contrary to law. The appeal instead turned on intervention: whether agricultural industry groups (“Associations”) and the Maumee Coalition II Association (“Coalition”) could intervene as defendants alongside U.S. EPA and Ohio EPA to defend the TMDL’s approval.

Key issue: under Federal Rule of Civil Procedure 24, when proposed intervenors share the government’s “ultimate objective” (upholding an agency action), what does it take to rebut the presumption that the government adequately represents their interests—especially where the intervenors want to defend the agency action using arguments the agency is unlikely (or institutionally unable) to make?

II. Summary of the Opinion

  • Associations: The Sixth Circuit reversed the denial of intervention of right and remanded with instructions to allow the Associations to intervene. The Associations rebutted the presumption of adequate representation by identifying a specific, case-relevant defense U.S. EPA was unlikely to assert: that certain regulatory/guidance “requirements” plaintiffs invoked are not required by the CWA’s “single, best meaning” (citing Loper Bright Enters. v. Raimondo).
  • Coalition: The Sixth Circuit affirmed denial of intervention of right and affirmed denial of permissive intervention. The Coalition failed to show inadequate representation because its defenses were either outside the proper scope of the APA challenge or likely to be raised by existing defendants (U.S. EPA and/or Ohio EPA).

The court also (1) reaffirmed the Sixth Circuit’s presumption-of-adequate-representation doctrine for private intervenors despite post-Berger developments, and (2) clarified that the Associations had not forfeited their key rebuttal argument because it was presented in reply and renewed during supplemental briefing, giving both the district court and opposing parties a fair chance to address it.

III. Analysis

A. Precedents Cited (and How They Shaped the Holding)

1. CWA cooperative federalism backdrop

  • Arkansas v. Oklahoma: Used to frame the CWA’s state–federal “partnership” and the statutory TMDL architecture (state establishes; U.S. EPA approves/disapproves). This context explains why many stakeholders (municipalities, agriculture, environmental groups) have strong interests, but it did not directly resolve Rule 24.
  • Env't L. & Pol'y Ctr. v. U.S. EPA: Supplies procedural history showing how the Maumee/Lake Erie impairment listing and the eventual TMDL arose from prolonged litigation and mediation—supporting the court’s later sensitivity to delay from additional parties.

2. Intervention standards and appellate review

  • Purnell v. City of Akron: Cited for the collateral-order rule—denials of intervention are immediately appealable.
  • Wineries of the Old Mission Peninsula Ass'n v. Township of Peninsula ("WOMP"): Provides the four-part Rule 24(a)(2) test and de novo review (except timeliness). Also supports the “expansive notion” of “interest” sufficient for intervention.
  • United States v. Michigan: Central to the “presumption of adequate representation” when intervenor and existing party share the same “ultimate objective,” and to the requirement that proposed intervenors articulate why representation is inadequate given “the scope of the issues” in the litigation.

3. The “minimal burden” vs. the presumption of adequacy

  • Trbovich v. United Mine Workers: Establishes that showing representation “may be” inadequate is a “minimal” burden. The Sixth Circuit reconciled Trbovich with its own presumption doctrine by emphasizing that even when ultimate objectives align, different “approach[es]” and “concerns” can warrant intervention.
  • Grutter v. Bollinger: Used to support rebuttal of the presumption when intervenors identify “specific relevant defenses” the existing party may not present.
  • Bradley v. Milliken: Reinforces the presumption doctrine; also used in the opinion’s discussion distinguishing when remand is needed for undeveloped factors.
  • Mich. State AFL-CIO v. Miller: Key support for the idea that it “may be enough” to show the existing party will not make all of the intervenor’s arguments; also used for minimal impairment burden and the “target of regulations” rationale (“differ markedly”).
  • Jordan v. Mich. Conf. of Teamsters Welfare Fund: Identifies rebuttal pathways (collusion, adversity, divergent arguments/interest).

4. Presumption after Berger

  • Berger v. North Carolina State Conference of the NAACP: The Associations argued Berger undermined presumptions generally. The Sixth Circuit read Berger narrowly: it rejects a presumption when a duly authorized state agent seeks to intervene to defend state law, and it expressly left open whether presumptions apply in other contexts. Therefore, Sixth Circuit precedent remains binding for private-party intervention alongside federal agencies.

5. Divergent-argument rebuttal illustrated: the decisive analogy

  • Jansen v. City of Cincinnati: The court’s most important factual analogue. There, intervenors rebutted adequacy because they would defend the challenged practices using an argument the city would not make due to a conflict: intervenors claimed the city’s test violated a decree, while the city would not. In Lucas County, the Associations likewise sought to defend the agency action by arguing certain agency-imposed “requirements” are not required by statute—an argument U.S. EPA was unlikely to advance because it would undermine its own regulatory framework.

6. APA record and “post hoc rationalizations”

  • Motor Vehicle Mfrs. Ass'n, Inc. v. State Farm Mut. Auto. Ins. Co. and DHS v. Regents of the Univ. of Cal.: Invoked by opponents of intervention to argue the Associations’ defenses were impermissible “post hoc rationalizations.” The court distinguished them: the Associations were not proposing new factual rationales outside the record; they were proposing a different legal view of what the CWA requires for a lawful approval decision.
  • Loper Bright Enters. v. Raimondo: Used to frame the Associations’ statutory-meaning argument. The court accepted that district courts are not bound by the agency’s statutory interpretation and can consider the statute’s “single, best meaning.”

7. Forfeiture vs. waiver and issue preservation

  • Berkshire v. Dahl: Used to distinguish forfeiture from waiver (no affirmative abandonment here).
  • Thomas M. Cooley L. Sch. v. Kurzon Strauss, LLP, Dice Corp. v. Bold Techs., and Rice v. Jefferson Pilot Fin. Ins. Co.: Provide the “timely and reasoned presentation” standard to avoid forfeiture.
  • Hamer v. Neighborhood Hous. Servs. of Chi. and Cockrun v. Berrien County: Cited to reinforce careful terminology and modern doctrine distinguishing waiver/forfeiture.

8. Permissive intervention discretion

  • Michigan and Purnell: Frame abuse-of-discretion review for Rule 24(b).
  • Buck v. Gordon and League of Women Voters of Mich. v. Johnson: Require sufficient explanation to permit meaningful review, unless obvious from the record.
  • Tahfs v. Proctor: Supplies the “definite and firm conviction”/clear error-of-judgment standard.
  • Bay Mills Indian Cmty. v. Snyder: Supports considering intervention-of-right factors when denying permissive intervention.
  • Ohio v. U.S. EPA: Quoted for the idea that adding premature/irrelevant arguments can “unnecessarily complicate” and delay complex agency litigation.

9. Scope-of-case and likely-defenses: why the Coalition lost

  • The court cited multiple district court cases—Nw. Env't Advocs. v. U.S. EPA, Food & Water Watch v. U.S. EPA, Bravos v. Green, and City of Arcadia v. U.S. EPA—to illustrate that U.S. EPA routinely raises jurisdictional/scope defenses in TMDL challenges, undermining the Coalition’s claim that its defenses would be uniquely presented.

B. Legal Reasoning

1. The “ultimate objective” triggers the presumption

The court reaffirmed that the presumption of adequate representation applies when the proposed intervenor and an existing party share the same litigation objective. Here, both U.S. EPA and the proposed intervenors sought the same outcome: upholding U.S. EPA’s approval of the Maumee TMDL. The court rejected attempts to defeat the presumption by pointing to broader, extra-litigation differences (e.g., agencies’ general administrative interests or other disputes in permitting), emphasizing that the “ultimate objective” is assessed at the level of the case at hand.

2. The controlling rebuttal principle: specific in-scope arguments + conflict/incentive not to raise them

Synthesizing Jansen, Grutter, Mich. State AFL-CIO, and Michigan, the court articulated (in substance) a practical test: to rebut the presumption, a proposed intervenor must identify (1) specific arguments within the scope of the case that it intends to raise, and (2) a reason the existing party may not or will not raise them, often due to a conflict of interest or institutional incentives.

3. Why the Associations satisfied rebuttal (and intervention of right)

The Associations’ proposed defense was not merely “we support the agency.” It was: even if the Maumee TMDL arguably falls short of certain regulatory/guidance-driven “required elements” alleged by plaintiffs, the CWA itself—under its “single, best meaning” (Loper Bright Enters. v. Raimondo)—does not require those elements for a lawful approval. That matters because:

  • It is in-scope: Plaintiffs alleged the approval was “not in accordance with law” (5 U.S.C. § 706(2)(A)), so statutory meaning of 33 U.S.C. § 1313(d) is directly relevant.
  • U.S. EPA is unlikely to make it: The agency would have to suggest its own regulations impose requirements beyond what the statute demands—an argument that undermines its regulatory program and litigation position. The court treated this as a conflict/incentive divergence akin to Jansen.
  • Not a forbidden post hoc rationale: The Associations were not adding new facts outside the record; they were offering a different legal framework for judging whether the existing record-based approval suffices.

Having found inadequate representation, the court also independently satisfied itself that the Associations had (a) a substantial interest (increased regulatory burdens likely if the TMDL is set aside and replaced with a more stringent one) and (b) minimal impairment (including the precedential effect of an adverse decision), consistent with WOMP and Mich. State AFL-CIO.

4. Why the Coalition failed rebuttal

The Coalition pointed to (i) possible divergence stemming from other U.S. EPA–Ohio EPA permitting disputes, and (ii) “additional defenses” such as jurisdiction/exhaustion/state-law review limits. The court found:

  • Other disputes were too collateral to show divergent litigation strategy on the “scope of the issues” in this APA case (Michigan).
  • Some defenses were out of scope (e.g., implying APA plaintiffs must exhaust state administrative remedies before the Ohio Environmental Review Appeals Commission).
  • Any in-scope scope-limiting defenses were likely to be raised by U.S. EPA and/or Ohio EPA anyway, and the Coalition did not show a “legitimate and reasonable concern” they would not (Grutter).

5. Permissive intervention: expertise is not enough when it adds complexity without unique, relevant contribution

For Rule 24(b), the court credited the Coalition’s “substantial expertise” but upheld the district court’s conclusion that adding another party in an already complex, multi-party APA record review would “unnecessarily complicate” and delay the case (quoting Ohio v. U.S. EPA). The Sixth Circuit emphasized the binary nature of APA relief here—set aside the approval or not—and noted amicus participation as the appropriate vehicle for practical-impact arguments not tied to unique legal defenses.

C. Impact

1. Expanded pathway for regulated entities to intervene in APA defenses

The decision strengthens an intervention playbook for regulated parties in APA cases: if the agency’s defense will track its own regulations and guidance, a regulated intervenor may intervene of right by advancing a statutory-meaning defense that narrows what the statute requires, especially where the agency is unlikely to argue its own rules are unnecessary or over-demanding.

2. Post-Loper Bright intervention stakes

By expressly crediting a defense framed around the statute’s “single, best meaning” (Loper Bright Enters. v. Raimondo), the court anticipates a litigation environment where challengers and defenders alike press pure statutory arguments untethered to agency deference. Intervention becomes more important because agencies may avoid arguments that destabilize their regulatory regime, while regulated parties may welcome them.

3. Preservation lesson: intervenors should articulate unique defenses early—but replies and supplemental briefing can suffice

The court’s forfeiture analysis signals that intervenors should identify divergent arguments as soon as practicable, but also that a well-developed reply—especially when supplemented by court-ordered additional briefing—can preserve the point for appeal (per Thomas M. Cooley L. Sch. v. Kurzon Strauss, LLP and related cases).

4. Limits: “unique” defenses must be both relevant and truly unlikely to be raised

The Coalition’s loss is as instructive as the Associations’ win. Merely adding defenses, asserting expertise, or pointing to generalized policy interests will not rebut adequacy when existing governmental defendants have every incentive and capacity to raise the same scope and jurisdiction arguments.

IV. Complex Concepts Simplified

  • TMDL (Total Maximum Daily Load): A pollution “budget” for an impaired waterbody: the maximum pollutant amount the water can receive while still meeting water quality standards (33 U.S.C. § 1313(d)).
  • Point vs. nonpoint sources: “Point sources” are discrete discharges (e.g., pipes) often addressed via permits; “nonpoint sources” are diffuse runoff (e.g., agricultural runoff). Federal regulations describe “wasteload allocations” (point sources) and “load allocations” (nonpoint sources). (40 C.F.R. § 130.2).
  • APA “arbitrary and capricious” review: A court reviews the agency’s decision based on the administrative record and asks whether the decision was reasonable and lawful (5 U.S.C. § 706(2)(A)).
  • “Post hoc rationalizations”: New factual explanations invented after the decision, not found in the record, cannot be used to defend agency action (citing DHS v. Regents of the Univ. of Cal. and Motor Vehicle Mfrs. Ass'n, Inc. v. State Farm Mut. Auto. Ins. Co.). Here, the court distinguished new facts from new legal arguments about what the statute requires.
  • Intervention of right vs. permissive intervention: Under Rule 24(a)(2), the court must allow intervention if the requirements are met; under Rule 24(b), the court has discretion and must consider delay and prejudice.
  • Presumption of adequate representation: If an intervenor and an existing party want the same outcome, courts presume the existing party adequately represents the intervenor. The presumption can be rebutted by showing the intervenor will make arguments the party won’t, often due to conflicting interests.

V. Conclusion

Lucas Cnty. Bd. of Comm'rs v. EPA establishes a significant Sixth Circuit intervention principle for APA litigation: when a regulated entity seeks to defend an agency action, it may intervene of right—even alongside the agency—if it can identify specific, case-relevant statutory arguments the agency is unlikely to raise because they conflict with the agency’s institutional interest in defending its own regulatory framework. The opinion simultaneously reinforces the continued vitality of the Sixth Circuit’s presumption-of-adequate-representation doctrine for private parties (notwithstanding Berger), while drawing a clear line: proposed intervenors must show not just additional viewpoints or expertise, but genuinely distinct defenses within the case’s scope that would otherwise likely go unmade.