By Brent Rosser, a partner, and Kate Perkins, an associate, with Hunton Andrews Kurth in its Charlotte, NC office.

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In nearly every major federal environmental statute enacted since the 1970s, including the Clean Water Act, Congress has included a “citizen suit” provision that allows individuals or groups to assert statutory claims alleging violations and to seek injunctive relief, civil penalties, and attorneys’ fees.1  However, because Congress intended environmental enforcement to fall primarily to the government,2 it also included “diligent prosecution” provisions making clear that citizen suits may be brought only in limited circumstances—namely, when the state or the United States Environmental Protection Agency (EPA) “cannot or will not command compliance.”3  As the Supreme Court has explained, this “bar on citizen suits when governmental enforcement action is under way suggests that the citizen suit is meant to supplement rather than to supplant governmental action.”4  Despite this admonition, some recent federal court decisions have allowed citizens suits to proceed despite ongoing government enforcement efforts, elevating the citizen-suit device beyond the supplemental role that Congress originally intended.

Background of Clean Water Act Diligent Prosecution

The Clean Water Act includes two diligent prosecution provisions that limit citizen suits—one that applies if EPA or a state “has commenced and is diligently prosecuting a civil or criminal action in [federal or state court] to require compliance with the standard, limitation, or order,” and another that applies where a state “has commenced and is diligently prosecuting” an administrative action “under a State law comparable to” the Act.5 

Historically, courts have deferred to agencies when assessing the diligence of government enforcement actions and have placed a heavy burden on citizens to overcome this presumption of diligence.6  In assessing diligence, courts examine whether the agency action “is capable of requiring compliance with the Act and is in good faith calculated to do so.”7  But the agency enforcement may be diligent without seeking the maximum penalties and compliance measures available, and the government action “need not be ‘far-reaching or zealous.’”8

Citizen suit plaintiffs cannot overcome the presumption of diligence by showing that their prosecution strategy is more aggressive than the agency’s.9  And courts have often granted deference where violations are settled pursuant to a consent decree with a schedule of compliance, so as to avoid interpreting the citizen suit provisions in a way that “‘would undermine the [government’s] ability to reach voluntary settlements with defendants.’”10  As one court explained, “[t]he Government . . . usually is in the best position to vindicate societal rights and interests.”11

Recent Caselaw

The First and Fourth Circuits have recently narrowed their interpretations of the Clean Water Act’s administrative action diligent prosecution provision.  Both circuits have construed the provision to allow citizen suits to proceed even where there was no serious contention that the state agency’s enforcement efforts lacked diligence.

In Blackstone Headwaters Coalition, Inc. v. Gallo Builders, Inc., 32 F.4th 99 (1st Cir. 2022) (en banc), an en banc First Circuit overturned 30-year precedent and held that 33 U.S.C. § 1319(g)(6)(A) bars citizen suits that seek civil penalties for ongoing violations of the Clean Water Act, but does not bar citizen suits for declaratory and injunctive relief.12  The court rejected its prior holding that this interpretation would improperly “‘lead to deferring to the primary enforcement responsibility of the government only where a penalty is sought in a civilian action, as if the policy considerations limiting civilian suits were only applicable within that context.’”13  The court instead reasoned that a “court which entertains a citizen action for injunctive relief can manage the action so as to ensure that the diligently pursued State enforcement action will dominate and that the [defendant] will not be whipsawed by multiple actions.”14 

The court acknowledged that the record “indisputably showed” that the state was diligently prosecuting its enforcement action.15  The court nevertheless interpreted § 1319(g)(6)(A) to allow a citizen suit for injunctive relief to proceed, where the state agency and the defendant had already entered into a consent order that required civil penalties, remedial measures to address the same violation that the citizen suit alleged, and stipulated penalties for any noncompliance.16 

In Naturaland Trust v. Dakota Finance, LLC, 41 F.4th 342 (4th Cir. 2022), a split Fourth Circuit panel held that a citizen suit filed after the state agency issued a Notice of Alleged Violation, but one month before the landowners’ consent decree with the agency was finalized, could proceed.17  The consent order imposed a civil penalty and required the landowners to obtain a National Pollutant Discharge Elimination System permit, submit stormwater and site stabilization plans, conduct a stream assessment, and perform any recommended remediation.18  Like Blackstone, there was “no serious argument that [the agency] failed to diligently prosecute the enforcement proceedings.”19  Nonetheless, the court held that the suit can proceed because the Notice of Alleged Violation did not technically “commence” an action under § 1319(g)(6)(A) before the citizen suit was filed.20 

As Judge Quattlebaum explained in dissent, however, the majority did “not address the common understanding of the word ‘commence,’”21 under which a Notice of Alleged Violation is “the first step the agency takes in enforcing its environmental laws.”22  According to Judge Quattlebaum, “the Clean Water Act’s cooperative federalism framework encourages states to experiment with different regulatory approaches,” and “[u]nder that framework, the state’s view of what commences its proceeding should be respected.”23  “By permitting the citizen suit here to proceed despite the measures [the state] had already taken, the majority’s decision elevates citizen suits above their supplemental role.”24

Potential Implications

Defendants may face challenges in some courts in light of these recent decisions allowing citizen suits to proceed despite diligent prosecution by the government.  Not only does narrowly construing diligent prosecution provisions elevate citizen suits above the supplemental role that Congress intended, but it may also have the unintended consequence of discouraging government enforcement.  In particular, some government agencies may be less inclined to pursue enforcement or otherwise resolve alleged violations if citizens are likely to file their own suits and second-guess that enforcement.  To avoid these consequences, as well as duplicative and potentially inconsistent enforcement, federal environmental statutes should be construed (as they are in the majority of jurisdictions) to promote the government as the primary enforcer, consistent with Congress’s original intent.  


  1. 33 U.S.C. § 1365(a) (Clean Water Act citizen suit provision).  See also, e.g., 42 U.S.C. § 7604(a) (Clean Air Act citizen suit provision); 42 U.S.C. § 6972(a) (Resource Conservation and Recovery Act citizen suit provision); 42 U.S.C. § 9659(a) (Comprehensive Environmental Response, Compensation, and Liability Act citizen suit provision).
  2. For example, the preamble to the Clean Water Act explains that states hold “the primary responsibilities and rights” in managing water resources.  33 U.S.C. § 1251(b).
  3. Gwaltney of Smithfield, Ltd. v. Chesapeake Bay Found., Inc., 484 U.S. 49, 62 (1987).
  4. Id. at 60.
  5. 33 U.S.C. § 1365(b)(1)(B); id. § 1319(g)(6)(A).
  6. Piney Run Pres. Ass’n v. Cnty. Comm’rs of Carroll Cnty., 523 F.3d 453, 459 (4th Cir. 2008) (explaining that “diligence is presumed”); Sierra Club v. Two Elk Generation Partners, Ltd. P’ship, 646 F.3d 1258, 1269 (10th Cir. 2011) (noting that “plaintiffs must meet a high standard to demonstrate” non-diligence) (internal quotation marks omitted); Friends of Milwaukee’s Rivers v. Milwaukee Metro. Sewerage Dist., 382 F.3d 743, 760 (7th Cir. 2004) (explaining that “diligence on the part of the State is presumed”).
  7. Friends of Milwaukee’s Rivers, 382 F.3d at 760.
  8. See Two Elk Generation Partners, 646 F.3d at 1269 (quoting Karr v. Hefner, 475 F.3d 1192, 1197 (10th Cir. 2007)).
  9. See Ellis v. Gallatin Steel Co., 390 F.3d 461, 477 (6th Cir. 2004) (“[S]econd-guessing of the EPA’s assessment of an  appropriate remedy . . . fails to respect the statute’s careful distribution of enforcement authority.”); Friends of Milwaukee’s Rivers, 382 F.3d at 761 (explaining that citizen suits are not permitted “[m]erely because the State may not be taking the precise action [the plaintiff] wants it to or moving with the alacrity [the plaintiff] desires”) (internal quotation marks omitted).
  10. Piney Run Pres. Ass’n, 523 F.3d at 459 (quoting Karr, 475 F.3d at 1198); see Karr, 475 F.3d at 1197 (explaining that “[a]n [agency] unable to make concessions is unable to obtain them”) (internal quotation marks omitted); Ark. Wildlife Fed’n v. ICI Americas, Inc., 29 F.3d 376, 380 (8th Cir. 1994) (“It would be unreasonable and inappropriate to find failure to diligently prosecute simply because [the defendant] prevailed in some fashion or because a compromise was reached.”).
  11. Hudson River Fishermen’s Ass’n v. Cnty. of Westchester, 686 F. Supp. 1044, 1052 (S.D.N.Y. 1988).
  12. 32 F.4th at 110.
  13. Id. at 108 (quoting and rejecting N. & S. Rivers Watershed Ass’n v. Town of Scituate, 949 F.2d 551, 558 (1st Cir. 1991)).
  14. Id. (internal quotation marks omitted).
  15. Id. at 103.
  16. Id. at 101–02.
  17. 41 F.4th at 350.
  18. Id. at 345–46.
  19. Id. at 357 (Quattlebaum, J., dissenting).
  20. Id. at 350.
  21. Id. at 354 (Quattlebaum, J., dissenting).
  22. Id. at 353 (Quattlebaum, J., dissenting).
  23. Id. at 353–54 (Quattlebaum, J., dissenting).
  24. Id. at 351 (Quattlebaum, J., dissenting).