We consider a constitutional challenge to a Denver city ordinance banning a category of dogs commonly known as “pit bulls.” 1 Sonya Dias, Hilary Engel, and Sheryl White allege that the pit bull ban violates the Fourteenth Amendment because it: (1) is unconstitutionally vague on its face; and (2) deprives them of substantive due process. Before the plaintiffs had *1173 any opportunity to present evidence to support their claims, the district court dismissed both claims under Federal Rule of Civil Procedure 12(b)(6). On appeal, the plaintiffs argue that the district court erred by prematurely dismissing the case at the 12(b)(6) stage. We agree in part.
We conclude that the plaintiffs lack standing to seek prospective relief for either claim because they have not shown a credible threat of future prosecution. We also determine that the district court correctly dismissed the facial vagueness challenge because the pit bull ban is not vague in all its applications. However, taking the factual allegations in the complaint as true, the plaintiffs have plausibly alleged that the pit bull ban is not rationally related to a legitimate government interest. Accordingly, we conclude that the district court erred in dismissing the substantive due process claim insofar as the plaintiffs seek retrospective relief. Our jurisdiction arises under 28 U.S.C. § 1291, and we dismiss in part, affirm in part, reverse in part, and remand.
I
A
Section 8-55 of the Revised Municipal Code of the City and County of Denver (“the Ordinance”) provides:
Sec. 8-55. Pit bulls prohibited.
(a) It shall be unlawful for any person to own, possess, keep, exercise control over, maintain, harbor, transport, or sell within the city any pit bull.
(b) Definitions....
(2) A “pit bull,” for purposes of this chapter, is defined as any dog that is an American Pit Bull Terrier, American Staffordshire Terrier, Staffordshire Bull Terrier, or any dog displaying the majority of physical traits of any one (1) or more of the above breeds, or any dog exhibiting those distinguishing characteristics which substantially conform to the standards established by the American Kennel Club or United Kennel Club for any of the above breeds. The A.K.C. and U.K.C. standards for the above breeds are on file in the office of the clerk and recorder, ex officio clerk of the City and County of Denver, at City Clerk Filing No. 89457.
Denver, Colo., Rev. Mun.Code § 8-55.
2
The Ordinance has both civil and criminal components.
Colo. Dog Fanciers, Inc. v. City & County of Denver,
Violating the Ordinance is also a criminal offense. § 1 — 13(a) (“[W]henever any section of this Code or any section of a rule or regulation promulgated hereunder requires, prohibits or declares to be unlawful the doing of any act, any violation of such section is hereby declared to be a criminal violation.”);
Colo. Dog Fanciers,
Denver originally enacted the Ordinance in 1989.
Colo. Dog Fanciers,
On April 21, 2004, then-Governor Bill Owens signed House Bill 04-1279, which prohibited Colorado municipalities from enacting breed-specific legislation. See Colo.Rev.Stat. § 18 — 9—204.5(5)(a). Denver suspended enforcement of the Ordinance in compliance with the new law and filed a lawsuit in state court seeking a declaratory judgment that the law violated home rule provisions of the Colorado Constitution. The state court ruled in favor of Denver, and the City resumed enforcement of the Ordinance on May 9, 2005. According to the plaintiffs, Denver has impounded and killed at least 1,100 dogs since enforcement resumed.
B
Because this case reaches us following Denver’s successful motion to dismiss, we assume the truth of all well-pleaded facts in the plaintiffs’ complaint.
See Gann v. Cline,
Hilary Engel is also a former Denver resident and is the owner of a dog named Cysco. On May 5, 2005, while Engel still resided in Denver, her then-boyfriend was stopped by a Denver animal control officer *1175 while taking Cysco on a walk. The officer told Engel’s boyfriend that he intended to seize Cysco once the Ordinance was reinstated. • Engel took Cysco to the animal control office in an effort to determine whether Cysco was a pit bull as defined in the Ordinance. Following that evaluation, an animal control officer informed Engel that although Cysco was beautiful and friendly, the dog looked too much like a pit bull to remain in Denver. The officer allowed Engel forty-eight hours to remove Cysco from within City limits. Engel temporarily placed Cysco in a shelter outside Denver and eventually moved to Lakewood, Colorado, to seek refuge from the Ordinance. Engel spent more than $5,000 and forfeited the security deposit on her Denver apartment in the process. Like Dias, Engel does not allege that she and Cysco plan to move back to Denver.
Sheryl White, the third named plaintiff, is also a former resident of Denver who fears that her dog, Sherman, falls within the ambit of the pit bull ban. On December 15, 2005, Sherman was seized by an animal control officer responding to a report by a neighbor that White owned a pit bull. In addition to the seizure, a criminal summons was issued to White. Animal control officials impounded Sherman until December 23, 2005. At that point, White was allowed to retrieve Sherman on the condition that White remove the dog from Denver. White complied, and from that date until January 1, 2006, she lived with Sherman at her employer’s office in Little-ton.
Pursuant to § 8 — 55(f) of the Ordinance, White demanded a hearing in order to force Denver to prove by a preponderance of the evidence that Sherman was a pit bull as defined in the Ordinance. The hearing officer, relying on evaluations by the three dog identification “experts” from the animal control office, determined that Sherman was a prohibited dog. From what we can glean from the complaint, the evaluations had been completed prior to the hearing. White requested a copy of these evaluations but animal control refused to disclose the' documents because they contained “internal information.” Then, on the day designated for White’s criminal trial, Denver dismissed all charges. White thereafter returned with Sherman to Denver until October 2007 when she relocated to Belton, Texas. White does not allege an intention to return to Denver with Sherman.
On April 6, 2007, Dias, Engel, and White filed this 42 U.S.C. § 1983 lawsuit on behalf of themselves and others similarly situated. 3 They claimed the Ordinance was vague on its face and that it deprived them of procedural due process, substantive due process, and equal protection of the laws. As defendants, the complaint named the City and County of Denver, and several officials: the Mayor, the Manager of the Department of Environmental Health, the Director of the Division of Animal Care and Control, and the Supervisor of Animal Control Investigators (collectively “Denver”) in both their official and individual capacities. The complaint sought injunctive and declaratory relief, damages, and attorneys’ fees. Denver moved to dismiss for failure to state a claim under Federal Rule of Civil Procedure 12(b)(6). 4
*1176
On March 20, 2008, without permitting oral argument on the motion, the district court dismissed all claims.
Dias v. City & County of Denver,
No. 07-cv-00722-WDM-MJW,
II
Although the district court did not address the plaintiffs’ standing to seek prospective relief,
6
standing is a component of this court’s jurisdiction, and we are obliged to consider it sua sponte to ensure the existence of an Article III case or controversy.
PeTA v. Rasmussen,
To the extent the plaintiffs seek prospective relief, we conclude that they lack standing because they have not alleged a credible threat of future prosecution under the Ordinance.
See Ward v. Utah (‘Ward I”),
In the context of a facial challenge to the constitutionality of a penal statute, a plaintiff alleges a continuing injury if “there exists a credible threat of [future] prosecution thereunder.”
7
Ward I,
As in
Rasmussen,
the plaintiffs have not demonstrated a continuing injury because they have not alleged a credible threat of future prosecution under the Ordinance.
To the extent plaintiffs seek retrospective relief from injuries already caused, however, they have standing. Dias and Engel both suffered actual injuries because they were forced to move from Denver to avoid the reach of the Ordinance. White suffered actual injury when her dog, Sherman, was seized by animal control officers, and when she was charged with a criminal violation of the Ordinance. Thus, each plaintiff has alleged an injury in fact supporting retrospective relief.
See Rasmussen,
Ill
We review de novo a district court’s dismissal under Federal Rule of Civil Procedure 12(b)(6).
Teigen v. Renfrow,
IV
Plaintiffs claim that the Ordinance violates the Due Process Clause of the Fourteenth Amendment because it is unconstitutionally vague on its face.
10
Specifically,
*1179
the plaintiffs contend that two parts of the Ordinance are impermissibly vague: (1) the criminal prohibition against owning “any dog that is an American Pit Bull Terrier, American Staffordshire Terrier, [or] Staffordshire Bull Terrier ... or any dog exhibiting those distinguishing characteristics which substantially conform to the standards established by the American Kennel Club or United Kennel Club for any of the above breeds”; and (2) the prohibition against owning “any dog displaying the majority of physical traits of any one ... or more of the above breeds.” Denver, Colo., Rev. Mun.Code § 8-55(b)(2). Because neither portion of the Ordinance is impermissibly vague in all of its applications, we conclude that the district court properly dismissed the plaintiffs’ vagueness challenge.
See Hoffman Estates,
“As generally stated, the void-for-vagueness doctrine requires that a per nal statute define the criminal offense with sufficient definiteness that ordinary people can understand what conduct is prohibited and in a manner that does not encourage arbitrary and discriminatory, enforcement.”
Kolender v. Lawson,
“Facial challenges are strong medicine.”
Ward v. Utah (‘Ward II”),
Insofar as the plaintiffs claim the AKC and UKC standards contain some elements that are vague and subjective, that may be true. But as we further explain below, a statute with some arguably vague elements is not automatically vague on its face in violation of the Fourteenth Amendment. Plaintiffs direct us to the AKC and UKC breed standards as incorporated by reference in the Ordinance. See, e.g., Official UKC Breed Standard, American Pit Bull Terrier, Appellant Br. Ex. 4 (“[t]he American Pit Bull Terrier is a medium-sized, solidly built, short-coated dog with smooth, well-defined musculature”; “[t]he skull is large, flat or slightly rounded, deep, and broad between the ears”; “[t]he neck is of moderate length and muscular”); AKC American Stafford-shire Terrier Breed Standard, Appellant Br. Ex. 1 (the head is “[m]edium length, deep through, broad skull, very pronounced cheek muscles, distinct stop”; the shoulders are “[s]trong and muscular with blades wide and sloping”; the back is “[flairly short”). Plaintiffs point out that some of the standards are framed in terms of preferences, see, e.g., Official UKC Breed Standard, Staffordshire Bull Terrier, Appellant Br. Ex. 3 (“Dark eyes are preferred, but may bear some relation to coat color”; “[acceptable [coat] colors include red, fawn, white, black, any shade of brindle, and blue, with or without white. Serious Faults: Black and tan or liver”), and claim that at least with respect to dog owners who are not breeders, determining whether a dog is prohibited would be a difficult task.
Even so, plaintiffs’ counsel conceded at oral argument that these standards can clearly fit a pure breed American Pit Bull Terrier, American Staffordshire Terrier, or Staffordshire Bull Terrier, registered as such with the AKC or UKC. Such a registered pure breed would unquestionably qualify as a prohibited dpg under the Ordinance.
See Sun,
y
Plaintiffs’ final contention is that the Ordinance deprives them of substantive due process. First, they allege that the human/companion animal bond is a funda *1181 mental liberty interest, and because the Ordinance is not narrowly tailored to serve a compelling government interest, it imposes an unconstitutional burden on this fundamental right. Second, even if a fundamental liberty interest is not implicated, the plaintiffs contend the Ordinance irrationally treats pit bulls and their owners in a different fashion than other dogs and owners because there is a lack of evidence that the prohibited animals pose a threat to public safety or constitute a public nuisance.
“[T]he touchstone of due process is protection of the individual against arbitrary action of government.”
County of Sacramento v. Lewis,
A
At the outset, plaintiffs claim that the human/companion animal bond is a fundamental liberty interest triggering strict scrutiny. In order to show that the human/companion animal bond is a fundamental right, we undertake a two-part inquiry. First, we “carefully describe the asserted fundamental liberty interest.”
Seegmiller,
The district court properly refrained from applying strict scrutiny to the Ordinance. Plaintiffs’ complaint is devoid of any factual allegations which would lend support to a conclusion that the human/companion animal bond is a fundamental liberty interest. Quite to the contrary, the nature and history of the relationship between the plaintiffs and their dogs is not raised in the complaint. Because of such failure, we do not further pursue a strict scrutiny analysis.
*1182 B
1
Even if the Ordinance does not implicate a fundamental right, it must nonetheless bear a rational relationship to a legitimate government interest.
Glucksberg,
However, the “shocks the conscience” standard is not applicable to cases in which plaintiffs advance a substantive due process challenge to a
legislative
enactment. Instead, it is an inquiry reserved for cases challenging
executive
action.
Lewis,
We held in
Seegmiller
that application of a “shocks the conscience” standard in cases involving
executive
action is not to the exclusion of the foregoing two-part framework for analyzing substantive due process challenges to legislation.
2
After careful review of the complaint, we conclude that the plaintiffs have alleged a substantive due process violation sufficient to survive a motion to dismiss for failure to state a claim. Viewing the factual allegations in the light most favorable to the plaintiffs, as we must, the complaint plausibly alleges that the Ordinance is not rationally related to a legitimate government interest. Although the plaintiffs may be unable to demonstrate through evidence that the Ordinance is irrational, the complaint makes out a claim for relief.
It is uncontested that Denver has a legitimate interest in animal control — the protection of health and safety of the public.
See Nicchia v. New York,
Pointing to the cases where courts across the country have rejected substantive due process challenges to pit bull bans,
see, e.g., Vanater,
We have no occasion to pass upon the ultimate merit of plaintiffs’ substantive due process challenge; that is not our role at this juncture. We are constrained to deciding if the complaint alleges facts sufficient to state a claim for relief. Whether the plaintiffs can marshal enough evidence to prevail on the merits of their claim that the Ordinance is irrational is a different matter entirely. But at the 12(b)(6) stage, we must assume that they can, even if it strikes us “that a recovery is very remote and unlikely.”
Twombly,
VI
In sum, because the plaintiffs have not alleged a credible threat of future prosecution under the Ordinance, they lack standing to seek prospective relief. To the extent plaintiffs seek such relief, we DISMISS those claims. We AFFIRM the district court’s dismissal of the vagueness claim. To the extent plaintiffs seek retrospective relief, we REVERSE the dismissal of the substantive due process claim and REMAND for further proceedings consistent with this opinion.
Notes
. Throughout this opinion, we follow the lead of the parties by referring to animals banned by this ordinance as "pit bulls.”
. American Kennel Club ("AKC”) and United Kennel Club ("UKC”) standards were not attached to the complaint filed in the district court. However, because the Ordinance itself incorporates those standards by reference, we take judicial notice of them.
See United States v. Williams,
. On October 1, 2007, the plaintiffs moved to certify the case as a class action pursuant to Federal Rule of Civil Procedure 23(b)(2). The district court did not act on the motion to certify prior to ruling on Denver’s motion to dismiss. Accordingly, in its order dismissing the case, the district court denied the motion to certify as moot. In light of our disposition, the district court will have to reconsider the motion for class certification on remand. We express no opinion on the merits of that motion!
. Denver also sought dismissal on the ground that the Colorado Supreme Court's decision *1176 in Colorado Dog Fanciers precluded the constitutional claims in this lawsuit. The district court declined to dismiss the case based on issue preclusion, however, because it concluded that the named plaintiffs were not in privity with the plaintiffs in Colorado Dog Fanciers. Denver has not appealed that ruling.
. Plaintiffs have not appealed the dismissal of the procedural due process or equal protection claims, therefore we do not address them.
. The district court did address the plaintiffs’ standing to bring their claim that Denver violated their procedural due process rights by relying upon unwritten policies. As the plaintiffs have not appealed the dismissal of that claim, we need not address their standing to raise it.
. In cases where the challenged statute threatens First Amendment freedoms, a plaintiff can demonstrate an injury in fact justifying prospective relief by alleging that the statute has a chilling effect on his or her speech.
See Initiative & Referendum Inst. v. Walker,
. The plaintiffs need not actually return to Denver with their dogs in order to have standing to seek prospective relief.
Bronson v. Swensen,
. We have frequently relied upon "affirmative assurances of non-prosecution from a governmental actor” as a basis for concluding that a plaintiff lacked standing to seek prospective relief.
Bronson,
. At oral argument, counsel for the plaintiffs insisted that the vagueness challenge was as-applied. We cannot agree. Although the language of the complaint is not entirely clear, it is most easily understood as a facial challenge. Moreover, in their response to the motion to dismiss, the plaintiffs acknowledged that their claim was one of facial vagueness. Pl.’s Resp. to Mot. to Dismiss, at 12 (“Plaintiffs’ Complaint alleges
facial vagueness
of provisions in the ordinance criminalizing ownership of dogs 'displaying the majority of physical characteristics’ of the prohibited breeds.” (emphasis added)). Although plain
*1179
tiffs failed to include this response in the appendix submitted to this court, the response was before the district court and thus remains a part of the record on appeal,
see
Fed. R.App. P. 10(a)(1), and we exercise our discretion in favor of considering it,
Milligan-Hitt v. Bd. of Trs.,
. Moreover, to the extent Denver contends that the shocks the conscience test has supplanted the rational basis test entirely, that contention is flatly inconsistent with
Seegmiller,
. Moreover, in the majority of cases where courts have sustained a pit bull ban as reasonable, they have done so based on a developed evidentiary record.
See, e.g., Vanater,
