F I L E D

United States Court of Appeals

Tenth Circuit

April 6, 2006

Elisabeth A. Shumaker

Clerk of Court

PUBLISH

UNITED STATES COURT OF APPEALS

TENTH CIRCUIT

STATE OF WYOMING,

Plaintiff-Appellant,

v. Nos. 04-8085 & 04-8087

WESLEY O. LIVINGSTON,

Defendant-Appellee.

STATE OF WYOMING,

Plaintiff-Appellant,

v.

MICHAEL DAVID JIMENEZ, 

Defendant-Appellee.

APPEAL FROM THE UNITED STATES DISTRICT COURT

FOR THE DISTRICT OF WYOMING

(D.C. NO. 04-CR-98J and 04-CR-103J)

Bryan A. Skoric, Park County and Prosecuting Attorney, Cody, Wyoming for

Plaintiff-Appellant State of Wyoming.

Michael S. Messenger, Messenger & Jurovich, P.C., Thermopolis, Wyoming for

Defendant-Appellee Livingston. 

Michael C. Johnson, Assistant United States Attorney (John W. Suthers, United

States Attorney for the District of Colorado, with him on the brief), Denver,

Colorado for Defendant-Appellee Jimenez.
1

In re McShane’s Petition, 235 F. Supp. 262 (N.D. Miss. 1964).

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Before O’BRIEN, McCONNELL, and ANDERSON, Circuit Judges.

McCONNELL, Circuit Judge.

This case involves a seldom-litigated corner of the constitutional law of

federalism known as Supremacy Clause immunity. Supremacy Clause immunity

governs the extent to which states may impose civil or criminal liability on

federal officials for alleged violations of state law committed in the course of

their federal duties. These disputes permit of no easy answers, because while

state criminal law provides an important check against abuse of power by federal

officials, the supremacy of federal law precludes the use of state prosecutorial

power to frustrate the legitimate and reasonable exercise of federal authority. The

doctrine has played a part in some of the most dramatic clashes between states

and the federal government in U.S. history, such as Mississippi’s prosecution of a

federal marshal for breach of the peace for using tear gas to control riots erupting

over the admission of the first African American student to its state university;1

California’s prosecution of a federal marshal for killing a former justice of the

state supreme court who he thought was about to assassinate Supreme Court
2

In re Neagle, 135 U.S. 1 (1890).

3

Idaho v. Horiuchi, 253 F.3d 359 (9th Cir. 2001) (en banc), vacated as

moot 266 F.3d 979 (9th Cir. 2001) (en banc).

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Justice Stephen Field;2 and, more recently, Idaho’s prosecution of a federal agent

for killing an unarmed woman (and a pet dog) in connection with the notorious

raid on a cabin at Ruby Ridge.3 This case involves the highly charged issue of

federal reintroduction of wolves in Wyoming. The question is whether the State

may prosecute the federal agent in charge of the wolf reintroduction program and

a federal contractor assisting him for alleged violations of the Wyoming laws

against trespass and littering, when the defendants unknowingly entered private

property in the course of tranquilizing and installing collar monitoring devices on

wolves that had strayed from their proper territory.

I. Background

In 1995, decades after the native population of gray wolves disappeared

from Wyoming, the United States Fish and Wildlife Service (“USFWS”)

embarked on a program of reintroduction of the animal to the State. Not

surprisingly for a State heavily dependent on livestock for its economic wellbeing, the decision to reintroduce wolves met with vehement local opposition,

which is well documented in the record. The USFWS recognized that the success

of the reintroduction program would depend, in large measure, on its ability to

control livestock predation by the reintroduced wolves. The USFWS uses radio
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telemetry to monitor and manage the wolves. USFWS staff capture the wolves

and outfit them with radio collars, which reveal the location of wolf packs to the

USFWS and enable the agency to use radio-signaled light and siren scare devices

to harass the wolves away from livestock and back to their designated territory.

The USFWS also provides the radio frequencies to local ranchers to alert them

when wolf packs are near.

Radio collaring wolves is not an easy process. Typically, a fixed wing

aircraft spots a wolf pack and ascertains whether any members of the pack lack

collars. If so, the pilot directs a helicopter team to the pack. When the pack

hears the helicopter, the wolves have a tendency to disperse in all directions. 

The helicopter pursues the wolves at low altitude to enable the gun operator to

fire a tranquilizer dart at a wolf from a distance of less than twenty yards. Once

struck by a dart, a wolf can still travel up to a mile before the tranquilizer takes

effect. This, along with the initial dispersion, means that collaring operations can

be spread over several square miles. When practicable, the helicopter will land to

pick up each immobilized wolf and take it to a central place where it can be

processed with other wolves; however, if landing is not possible, a team member

will hike to the wolf and either carry it to the central location or process it on the

spot. The tranquilized wolves require close attention. The tranquilizers prevent

the wolves from effectively regulating their body temperature, so capture teams
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have to move the wolves into open or shady areas as conditions dictate. The

wolves also have trouble closing their eyes and regulating incoming light while

under effect of the drugs.

Defendant Michael David Jimenez, Appellee in No. 04-8085, has been the

project leader of the USFWS Wyoming Wolf Recovery Project since 1999. His

prior experience includes participation in a capture team that radio collared 47

wolves in Yellowstone Park and supervision of a team that radio collared another

28 wolves. Defendant Wesley O. Livingston, Appellee in No. 04-8087, an

experienced wolf handler, was an employee of Hawkins and Powers Aviation, Inc.

working with Mr. Jimenez as a federal contractor to support the wolf monitoring

program. 

On February 13, 2004, a fixed wing aircraft spotted the Washakie pack, a

troublesome group of gray wolves, near Meeteetse, Wyoming, far outside their

normal range. This Court is familiar with the Washakie pack on account of

earlier litigation in which Wyoming ranching interests sought to compel the

USFWS to undertake greater efforts to control the pack. See Gordon v. Norton,

322 F.3d 1213, 1215 (10th Cir. 2003). The core of the Washakie pack’s territory

is north of Dubois, Wyoming in the Dunoir Valley. It is difficult for the USFWS

to control the pack through helicopter operations in the Dunoir Valley because of

rugged terrain, extensive forest cover, and frequent windy conditions. The
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spotting of the pack outside of its normal range presented an opportunity to collar

the wolves. Mr. Jimenez sought and received authorization from his supervisor,

Edward Bangs, to begin a capture operation. On February 14, 2004, Mr. Jimenez,

Mr. Livingston, and a helicopter pilot began the operation.

In accordance with USFWS procedure, it was Mr. Jimenez’s practice to

secure permission from land owners if he thought he would need to go on private

land. Of the members of the capture team, Mr. Jimenez was least familiar with

the Meeteetse area. Before the helicopter flight, Mr. Jimenez spoke with the

fixed-wing pilot and the helicopter pilot; they both indicated their belief that the

wolves were located on federal land managed by the Bureau of Land Management

(BLM). The area in which the wolves were spotted is a jumble of federal, state,

and private land; it is difficult from the air (and often from the ground) to

determine the ownership of the land, even with the assistance of maps. 

Determining the ownership of the land during the operation was all the more

difficult because the doors of the helicopter were removed to allow operation of

the dart and net guns; this made map reading impossible during flight because of

the wind blowing through the helicopter. The helicopter was equipped with a

global positioning system (GPS) that allowed the pilot to lock in coordinates

whenever a dart or net was fired. Later examination of GPS coordinates indicated
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that, at the time when darts or nets were discharged from the helicopter, the target

wolves were on private land. 

The operation successfully captured and collared five wolves. One wolf

was net gunned, physically restrained, radio collared, and released. Three wolves

were net gunned and then immobilized with darts and another wolf was darted on

a rocky slope where it was unsafe to land. The helicopter harassed this last wolf

down a hill toward a gravel road where it was safe for the helicopter to land.

After dropping Mr. Jimenez off on the road, the helicopter went to retrieve the

three other darted wolves. Mr. Jimenez walked up a hill to retrieve the

immobilized wolf. He carried this wolf down the slope to a shaded patch of snow

near the road. Later examination by state surveyors revealed that this spot was

outside the county road right of way, on private land owned by the Larsen Ranch. 

The helicopter returned with the three other wolves, which Mr. Jimenez and Mr.

Livingston moved to the patch of snow where the other darted wolf had been

deposited. At this point the helicopter left to refuel while Mr. Jimenez and Mr.

Livingston examined the wolves for injuries, took blood samples, and placed

radio collars on them. The wolves were released. A monitoring flight on

February 19, 2004 revealed that the Washakie pack had traveled about 15 miles

southwest of the processing spot; by March 4, 2004 the pack had returned to its

traditional range in the Dunoir Valley.
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In his declaration, Mr. Jimenez states that there were no fences, cattle,

notices of private property, or other postings at the site where he and Mr.

Livingston processed the wolves. He states that he was not familiar with the road

and no one had informed him that the area adjacent to the road was private

property. As Mr. Jimenez and Mr. Livingston were attending to the wolves,

Randy Kruger, a shareholder and employee of the Larsen Ranch Company, owner

of the property, drove up the road. He stopped his vehicle and asked Mr. Jimenez

what he was doing. Mr. Jimenez explained his purpose. Mr. Kruger never

informed Mr. Jimenez that he was on private land and never asked Mr. Jimenez to

leave Larsen Ranch property or to remove the wolves from ranch property. Mr.

Kruger had a camera and took several photographs of Mr. Jimenez and the

wolves, which appear in the record. After an apparently amicable conversation,

Mr. Jimenez and Mr. Kruger shook hands before Mr. Kruger departed. 

On March 2, 2004 Special Agent Steve Herrmann of the Wyoming Division

of Criminal Investigation began investigating allegations by Mr. Kruger that Mr.

Jimenez and Mr. Livingston had trespassed on Larsen Ranch land during the

capture operation. As part of this investigation Mr. Herrmann met with a Park

County Engineer and a Park County Works Department Project Manager to survey

the site of the encounter to determine whether Mr. Jimenez and Mr. Livingston

had been on private land during the operation. The road, Park County Road 4 CP,
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has a sixty foot right of way. The survey indicated that in two of the photographs

taken by Mr. Kruger, Mr. Jimenez was on Larsen Ranch land. Interviews with

Mr. Jimenez and Mr. Livingston confirmed the general outlines of Mr. Kruger’s

allegations and also revealed that Mr. Jimenez had walked approximately one

quarter mile north of the road to retrieve a darted wolf. 

On April 16, 2004, the State of Wyoming filed separate Misdemeanor

Informations in the Park County Circuit Court alleging that Mr. Jimenez and Mr.

Livingston violated Wyoming Statute § 6-3-303(a), which prohibits knowingly

entering the land of another without authorization, and Wyoming Statute § 6-3-

204(a), which prohibits littering by placing or depositing objects on the property

of another. Mr. Livingston appeared before the Circuit Court on May 11, 2004. 

Mr. Jimenez never appeared before the Circuit Court. Mr. Jimenez filed a notice

of removal in the United States District Court for the District of Wyoming on

May 4, 2004. The district court entered an order of removal pursuant to 28

U.S.C. § 1442(a)(1) on May 7, 2004. On May 10, 2004, Mr. Livingston filed a

notice of removal with the district court and the court entered an order of removal

pursuant to 28 U.S.C. § 1442(a)(1) on the same date.

The State of Wyoming filed motions to vacate the orders removing the

prosecutions. In both motions, the State argued that the federal court did not

have jurisdiction because the Defendants had not been arraigned and that removal
-10-

was improper because the district court did not hold an evidentiary hearing, as

required by 28 U.S.C. § 1446(c)(5). On May 27, 2004, Mr. Jimenez filed a

motion to dismiss, asserting that because federal law authorized his actions he

was entitled to immunity under the Supremacy Clause of the Constitution. On

June 8, 2004, Mr. Livingston filed a motion to dismiss, arguing that because he

was acting at the authorized direction of a federal officer, he was similarly

immune from prosecution under the Supremacy Clause. On June 30, 2004, the

district court held a combined hearing on the motions to vacate removal and the

motions to dismiss. On July 16, 2004, the district court issued an order denying

the motions to vacate and granting both motions to dismiss. 

The State of Wyoming appeals, raising two arguments. First, it contends

that the district court erred by denying the motion to vacate removal because the

district court did not hold an evidentiary hearing prior to ordering the removal. 

Second, it argues that the grant of Supremacy Clause immunity was improper

because there were contested issues of fact that were material to whether the

actions of the Defendants were necessary and proper to carry out their authorized

duties.

Before the district court and at appellate oral argument, Wyoming argued

that a grant of Supremacy Clause immunity was inappropriate for Mr. Livingston

because he was a federal contractor rather than a federal employee. However,
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Wyoming did not address this issue in its opening appellate brief. The issue is

therefore waived. See Lifewise Master Funding v. Telebank, 374 F.3d 917, 927

n.10 (10th Cir. 2004) (noting that an appellant waives the right to appeal any

rulings of the district court that it did not address in its opening appellate brief);

Fed. R. App. P. 28(a)(9)(A) (requiring that an appellant’s brief contain an

argument that includes “appellant’s contentions and the reasons for them”). 

Accordingly, for purposes of this case, we will treat Mr. Livingston as if he were

a federal officer. 

II. Applicable Law

A. The Development of Supremacy Clause Immunity

The framers of the American federal system expected the federal and state

governments each to check the abuses of the other. See The Federalist No. 28, at

179 (Alexander Hamilton) (Jacob E. Cooke ed., 1961) (“[T]he General [i.e.,

federal] Government will at all times stand ready to check the usurpations of the

state governments; and these will have the same disposition towards the General

Government. . . . If [the rights of the people] are invaded by either, they can

make use of the other, as the instrument of redress.”); The Federalist No. 51, at

351 (James Madison) (“In the compound republic of America . . . . a double

security arises to the rights of the people. The [state and federal] governments

will controul each other; at the same time that each will be controulled by
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itself.”). The flipside of this mutual checking function, however, is the danger

that one level of government would improperly restrict the other, and especially

that states would impede or frustrate the legitimate execution of federal law. To

prevent this second evil, federal officers have long been held immune from state

prosecutions for actions reasonable and necessary in the discharge of their federal

responsibilities. See, e.g., In re Neagle, 135 U.S. 1, 75 (1890); Ohio v. Thomas,

173 U.S. 276, 284 (1899). This immunity is rooted in the Supremacy Clause of

the United States Constitution, which provides:

This Constitution, and the Laws of the United States which shall be made

in Pursuance thereof; and all Treaties made, or which shall be made, under

the Authority of the United States, shall be the supreme Law of the Land;

and the Judges in every State shall be bound thereby, any Thing in the

Constitution or Laws of any State to the Contrary notwithstanding.

U.S. Const. art. VI, cl. 2. 

Although the Supremacy Clause explicitly refers only to the “Constitution”

and “Laws,” its implication is that states may not impede or interfere with the

actions of federal executive officials when they are carrying out federal laws. As

Chief Justice John Marshall maintained in the great case of McCulloch v.

Maryland, 17 U.S. (4 Wheat.) 316, 436 (1819), “the states have no power, by

taxation or otherwise, to retard, impede, burden, or in any manner control, the

operations of the constitutional laws enacted by congress to carry into execution

the powers vested in the general government.” It is not necessary for Congress to
-13-

provide expressly for such immunity in the statutes under which federal officials

act; Supremacy Clause immunity is “incidental to, and is implied in the several

acts by which these [federal] institutions are created, and is secured to the

individuals employed in them, by the judicial power alone.” Osborn v. Bank of

United States, 22 U.S. (9 Wheat.) 738, 865-66 (1824) (Marshall, C.J.). 

The Supreme Court’s leading case on Supremacy Clause immunity is In re

Neagle, 135 U.S. 1 (1890), in which the Court held that a deputy marshal was

immune from state prosecution for murder when he killed a man he suspected was

about to stab Justice Stephen Field. While Justice Field was riding circuit in

1888, two of the litigants, former California Chief Justice David Terry and his

wife, Sarah Terry, erupted in a violent outburst. Id. at 44-45. Mr. Terry punched

one of the marshals, knocking out his tooth, and then pulled a bowie knife from

inside his vest; Mrs. Terry attempted to draw a handgun from her handbag. Id. at

45-46. The Terrys were removed from the courtroom and sentenced to prison for

contempt of court. Id. at 45. Undeterred by their contempt sentence, the Terrys

issued threats against Justice Field that were “open, frequent, and of the most

vindictive and malevolent character.” Id. at 46. In response, the Attorney

General assigned Deputy United States Marshal David Neagle to accompany

Justice Field for his protection on his return to circuit duty in California in 1889. 

Id. at 51-52. Mr. Neagle was given special instructions to “attend upon Judge
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Field both in court and while going from one court to another, and protect him

from any assault that might be attempted upon him by [the] Terry[s].” Id. at 52. 

Justice Field, accompanied by Mr. Neagle, was traveling by railway from

Los Angeles to San Francisco when the Terrys boarded the train in Fresno. Id.

Justice Field was in the dining car when he encountered the truculent couple. Id.

at 52. Mrs. Terry left the dining car to obtain a revolver while Mr. Terry

assaulted Justice Field with his fists. Id. at 52-53. Mr. Neagle pointed his gun at

Mr. Terry and cried out, “Stop! Stop! I am an officer!,” whereupon Mr. Terry

reached into his clothing as if to pull out a weapon. Id. at 53. Mr. Neagle shot

him twice, killing him instantly. Id. It turned out that Mr. Terry had no weapons

on his person. Id. Mr. Neagle was charged with murder under California law in

the County of San Joaquin. Id. at 5. While a prisoner awaiting trial, he sought

and obtained from the federal court a writ of habeas corpus, which was affirmed

by the court of appeals and appealed to the Supreme Court by the Sheriff of San

Joaquin County. Id. at 3.

The Supreme Court held that Mr. Neagle was entitled to habeas corpus

relief because he was acting under authority of the law of the United States, and

thus he was “not liable to answer in the courts of California on account of his part

in that transaction.” Id. at 76. As a preliminary matter, the Court held that any

defenses Mr. Neagle might have under state law were not relevant to the federal
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court proceeding. Although “such [defenses] would be a proper subject for

consideration on a trial of the case for murder in the courts of the state of

California,” the Court explained, “there exists no authority in the courts of the

United States to discharge the prisoner . . . unless there be found in aid of the

defense of the prisoner some element of power and authority asserted under the

government of the United States.” Id. at 54. 

The Court then considered whether Mr. Neagle’s defense stemmed from the

exercise of federal authority. It rejected the argument that Mr. Neagle’s conduct

was unauthorized because no act of Congress expressly empowered marshals to

accompany Supreme Court justices through their circuits, to serve as their

bodyguards, and to defend them from assaults. Id. at 58. In doing so, the Court

explained that it is appropriate to “extend in a liberal manner the benefit of the

writ of habeas corpus to persons imprisoned for the performance of their duty.” 

Id. Ultimately, the Court derived federal power and authority for Mr. Neagle’s

conduct from the Attorney General’s authorization of a detail of marshals to

protect Justice Field during his trip to California. Id. at 67-68. 

After ascertaining that Mr. Neagle was authorized to protect the life of a

Supreme Court Justice, the only remaining inquiry was whether he did “no more

than what was necessary and proper” to carry out that duty. Id. at 75. Given the

past behavior of the Terrys, the Court concluded that Mr. Neagle’s belief that
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Justice Field’s life was in danger was “well-founded”and his actions “justified.” 

Id. at 76. Accordingly, the Court held that it was necessary and proper for him to

use lethal force against Mr. Terry, and affirmed the grant of habeas corpus. Id. 

The Court reaffirmed the principles of Neagle in Ohio v. Thomas, 173 U.S.

277 (1899). An Ohio statute, presumably pressed by dairy farmers, required any

establishment serving or using oleomargarine to prominently display that fact on a

large placard. Id. at 278. In disregard of this vital labeling law, the eating house

at the Central Branch of the National Home for Disabled Volunteer Soldiers

impetuously served oleomargarine without advertisement. Id. Unwilling to

countenance this affront to its laws, the State of Ohio indicted Mr. Thomas, the

governor in charge of the eating house. Id. at 277. Mr. Thomas was convicted of

the offense and the court ordered him imprisoned until he paid a $50 fine; he

refused to pay, and instead filed a writ of habeas corpus in the Southern District

of Ohio, which the court granted. Id. at 280. The Sixth Circuit affirmed and

Ohio appealed to the Supreme Court. The Court affirmed on the grounds that the

eating house was a federal facility and Mr. Thomas had authorization from the

Secretary of War to serve oleomargarine to his charges. Id. at 282. This holding

gives grants of federal authority a generous sway. Mr. Thomas was not

prosecuted for serving oleomargarine, but for failing to notify patrons he was

doing so. This requirement was not incompatible with Mr. Thomas’s federal
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authorization to serve oleomargarine; Mr. Thomas could have complied with the

state law without shirking his federal duty. Nevertheless, the Court concluded

that the grant of federal authority was sufficient not only to permit serving

oleomargarine, but to prevent Ohio from regulating the manner and circumstances

of service as well.

In both Neagle and Thomas it was apparent that the federal officers had

acted reasonably in discharging their duties. However, in United States ex rel.

Drury v. Lewis, 200 U.S. 1 (1906), the Court was confronted with the question

whether Supremacy Clause immunity applies when it is unclear whether officers

acted reasonably. Drury involved a state prosecution of two soldiers charged with

murdering a civilian. Id. at 2. The soldiers claimed that the shooting was lawful

because the suspect was in flight; witnesses testified that the soldiers had shot the

victim after surrender. Id. at 3-4. A federal circuit court refused to grant a writ

of habeas corpus to the soldiers at an early stage in the litigation. Id. at 6. The

Court affirmed, noting that only “exceptional” cases warrant exercise of the

“exceedingly delicate” jurisdiction of federal courts to usurp state prosecutions,

and finding that the circuit court properly exercised its discretion not to issue the

writ in advance of trial given the conflicting evidence about whether the killing

was lawful. Id. at 7-8. 
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The contrast between Lewis and Neagle clarifies the key inquiry in early

Supremacy Clause immunity cases: given the undisputed facts of a case, was the

federal officer reasonably discharging his authorized federal duties? If so, then a

grant of habeas corpus is appropriate in advance of trial. If not, then the state

court prosecution may proceed, leaving as recourse a post-conviction habeas

petition if the result is adverse. 

B. Supremacy Clause Immunity Doctrine in the Lower Federal Courts

The Supreme Court has decided no Supremacy Clause immunity case since

1920. See Johnson v. Maryland, 254 U.S. 51 (1920). Modern Supremacy Clause

immunity doctrine has thus largely been developed in the lower federal courts. In

Clifton v. Cox, 549 F.2d 722, 724 (9th Cir. 1977), the Ninth Circuit considered

whether a special agent for the Bureau of Narcotics and Dangerous Drugs was

entitled to immunity for a killing that occurred during a drug raid. After finding

that the federal agent’s acts were within the scope of his authority, the court went

on to consider whether the agent’s conduct “was necessary and proper under the

circumstances.” Id. at 728. The Ninth Circuit explained the “necessary and

proper” standard as follows: 

Determination of whether petitioner’s shooting . . . was necessary

and proper . . . must rest not only on the subjective belief of the

officer but also on the objective finding that his conduct may be said

to be reasonable under the existing circumstances. Proper

application of this standard does not require a petitioner to show that
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his action was in fact necessary or in retrospect justifiable, only that

he reasonably thought it to be. 

Id. The Ninth Circuit incorporated a subjective element into the “necessary and

proper” analysis. It explained that “‘if . . . petitioner shows . . . that he had an

honest and reasonable belief that what he did was necessary in the performance of

his duty . . . then he is entitled to the relief he seeks.’” Id. at 729 (quoting In re

McShane’s Petition, 235 F. Supp. 262, 274 (N.D. Miss. 1964)). 

In Kentucky v. Long, 837 F.2d 727 (6th Cir. 1988), the Sixth Circuit framed

the Supremacy Clause immunity analysis in a similar fashion. The court

explained: 

[A] two-part test determines whether or not a state court has

jurisdiction to prosecute a federal agent for conduct facially violative

of a state’s criminal code. Under Neagle, a state court has no

jurisdiction if (1) the federal agent was performing an act which he

was authorized to do by the law of the United States and (2) in

performing that authorized act, the federal agent did no more than

what was necessary and proper for him to do.

Id. at 744. As to whether an act was “necessary and proper,” the Sixth Circuit,

citing Clifton, stated that a federal officer must “only show that he reasonably

thought it to be necessary and justifiable.” Id. at 745. The court also included

Clifton’s subjective element, which requires the agent to “have an honest belief

that his action was justified.” Id. The Second Circuit has adopted a similar

approach. See New York v. Tanella, 374 F.3d 141, 147 (2d Cir. 2004); Whitehead

v. Senkowski, 943 F.2d 230, 234 (2d Cir. 1991) (“[T]he agent must have a
4McCulloch v. Maryland, 17 U.S. (4 Wheat.) 316, 421 (1819), provides the

canonical exposition of the meaning of “necessary and proper”: “Let the end be

legitimate, let it be within the scope of the constitution, and all means which are

appropriate, which are plainly adapted to that end, which are not prohibited, but

consist with the letter and spirit of the constitution, are constitutional.” This

cannot be the definition of Supremacy Clause immunity because it would imply

that federal officers are virtually unlimited in their choice of appropriate means

(including violation of state law) to carry out federal policy. As the cases

demonstrate, that is too broad an understanding of the immunity. While federal

officers sometimes are entitled to immunity for violations of state law, this is only

where they had an objectively reasonable and well-founded basis to believe that

their conduct was necessary for the performance of their federal duties, which

entails a more demanding judicial scrutiny of the relation of means to ends than is

appropriate under the Necessary and Proper Clause.

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subjective belief that his conduct was justified, and that belief must be objectively

reasonable.”).

Although we agree with the general Supremacy Clause immunity analysis

set forth in Clifton and Long, we are hesitant to adopt the “necessary and proper”

label as it may engender unnecessary confusion with the familiar Necessary and

Proper Clause of Article I, Section 8, Clause 18.4

 The “necessary and proper”

language is derived from Neagle, where the Court said,

if the prisoner is held in the state court to answer for an act which he

was authorized to do by the law of the United States, which it was his

duty to do as marshal of the United States, and if, in doing that act,

he did no more than what was necessary and proper for him to do, he

cannot be guilty of a crime under the law of the state of California.

In re Neagle, 135 U.S. at 75 (emphasis added). However, the Neagle Court also

used other language to describe its analysis. In explaining its grant of habeas
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relief, the Court emphasized that “Neagle was correct in the belief that, without

prompt action on his part, the assault of Terry upon the judge would have ended

in the death of the latter; [and] that, such being his well-founded belief, he was

justified in taking the life of Terry.” Id. at 76 (emphasis added). As other circuits

have found, the Court in Neagle was granting immunity for federal agents who

reasonably believed that their acts were necessary to perform their duties. 

Because it is equally appropriate and less confusing to label the second part of the

Supremacy Clause immunity analysis “reasonable and necessary,” we will use that

language wherever possible throughout the remainder of this opinion.

We are also concerned with the incorporation of a subjective element into

the reasonableness of a federal officer’s actions, an element that was not present

in the Supreme Court’s decisions. The subjective element first appeared in

district court decisions in the mid-twentieth century. In Brown v. Cain, 56 F.

Supp. 56, 58 (E.D. Pa. 1944), and McShane, 235 F. Supp. at 274, the courts held

that a federal officer must have an “honest[]” belief that his actions are

reasonable and necessary to the exercise of his authority. Although most circuit

courts have adopted the subjective approach without analysis, the en banc Ninth

Circuit has recently questioned whether inclusion of a subjective component is

appropriate in light of the Supreme Court’s decision in Harlow v. Fitzgerald, 457

U.S. 800, 817-18 (1982), which held that qualified immunity should depend on
-22-

whether the official acted in an objectively reasonable manner, without reference

to subjective intentions. Idaho v. Horiuchi, 253 F.3d 359, 366 n.11 (9th Cir.

2001) (en banc), vacated as moot, 266 F.3d 979 (9th Cir. 2001) (en banc). 

Although qualified immunity and Supremacy Clause immunity have

different sources and functions, there is a functional similarity between these two

doctrines. Both qualified immunity and Supremacy Clause immunity reduce the

inhibiting effect that a civil suit or prosecution can have on the effective exercise

of official duties by enabling government officials to dispose of cases against

them at an early stage of litigation. See Anderson v. Creighton, 483 U.S. 635, 638

(1987) (“[D]amages suits against government officials can entail substantial

social costs, including the risk that fear of personal monetary liability and

harassing litigation will unduly inhibit officials in the discharge of their duties.”);

Long, 837 F.2d at 752 (analogizing Supremacy Clause immunity to qualified

immunity and concluding that in both situations, courts have a duty to make early

rulings on immunity issues to avoid excessive interference with official actions). 

Just as the Supreme Court jettisoned the subjective element of the qualified

immunity test because it was incompatible with the goal of promptly determining

whether qualified immunity was appropriate on a motion for summary judgment,

Harlow, 457 U.S. at 815-819, it may also be appropriate to reject a subjective

element of the Supremacy Clause immunity test. Nonetheless, because Wyoming
5We also leave for another day whether federal officers are entitled to

Supremacy Clause immunity where their state law violation was disproportionate

to the federal policy they were carrying out – where, for example, they commit a

grievous state offense for the purpose of enforcing a trivial federal policy. 

Wyoming has not argued that its laws against trespassing and littering are so

significant that they outweigh the federal interest in wolf monitoring.

-23-

does not dispute that both Mr. Jimenez and Mr. Livingston subjectively believed

they were on federal land, we need not now decide whether a federal officer’s

subjective intent factors into the determination of whether an action was

reasonable and necessary.

In harmony with the Second, Sixth, and Ninth Circuits, we hold that a

federal officer is not entitled to Supremacy Clause immunity unless, in the course

of performing an act which he is authorized to do under federal law, the agent had

an objectively reasonable and well-founded basis to believe that his actions were

necessary to fulfill his duties. We leave for another day the question whether that

belief must be both subjectively and objectively reasonable.5

 

C. Congressional Protection of Federal Actors: Federal Officer Removal

Statutes

Related to the judicially created Supremacy Clause immunity doctrine are

federal officer removal statutes. Like Supremacy Clause immunity, federal

officer removal statutes are designed to protect the operations of the federal

government from state interference. Despite their similarities, the principles are

distinct. Supremacy Clause immunity, when properly established, provides an
6

 There is one notable exception to this pattern of reviewing grants of

habeas corpus. In Johnson v. Maryland, 254 U.S. 51, 57 (1920), the Court

reversed a Maryland conviction of a post office employee for driving without a

Maryland license. In a brief opinion reviewing the conviction on direct appeal,

Justice Holmes concluded that immunity was appropriate for the employee and

thus the conviction and fine were invalid. Id.

-24-

absolute immunity to prosecution. See Neagle, 135 U.S. at 75; Long, 837 F.2d at

752. Federal officer removal statutes, in contrast, provide federal officers with a

federal forum for the entire trial, including determinations of guilt or innocence

as well as the applicability of official immunity. This protects against the

possibility of a hostile state forum, which might arise when the federal officer is

enforcing a locally unpopular national law. See Willingham v. Morgan, 395 U.S.

402, 407 (1969) (“[O]ne of the most important reasons for removal is to have the

validity of the defense of official immunity tried in a federal court.”); Tennessee

v. Davis, 100 U.S. (10 Otto) 257, 263 (1880) (“[The federal government] can act

only through its officers and agents, and they must act within the States. If, when

thus acting, and within the scope of their authority, those officers can be arrested

and brought to trial in a State court, for an alleged offense against the law of the

State . . . the operations of the general government may at any time be arrested at

the will of one of its members.”). Although early Supremacy Clause immunity

cases were based on habeas corpus statutes that provided for a grant of the writ

where officers acted under the authority of federal laws,6

 such cases now usually
-25-

arise on motions to dismiss after the case has been removed to federal court. See

Long, 837 F.2d at 730; Horiuchi, 253 F.3d at 364; Tanella, 374 F.3d at 142. Not

all cases involving prosecutions of federal officers, however, permit of removal,

see Mesa v. California, 489 U.S. 121, 139 (1989), and the history of cases

involving federal officer removal statutes demonstrates the circumstances under

which removal is appropriate.

Although they have not always taken their present form, federal officer

removal statutes have long been a part of this country’s history. The first removal

provision was enacted as part of an 1815 customs statute, which attempted to

enforce, over the opposition of New England states, an embargo on trade with

England. Willingham v. Morgan, 395 U.S. 402, 405 (1969). The removal statute

“allowed federal officials involved in the enforcement of the customs statute to

remove to the federal courts any suit or prosecution commenced because of any

act done ‘under colour’ of the statute.” Id. The 1815 removal statute expired at

the end of the war, but a new removal statute protecting federal officers who were

enforcing customs laws was passed in 1833 in response to South Carolina’s

threats of nullification. Id. With the Civil War came other removal statutes,

authorizing removal of civil suits and criminal prosecutions arising out of

enforcement of federal revenue laws. Id. at 405-06. 
-26-

These early removal statutes were often met with constitutional challenges,

based on the theory that the cases did not arise under the Constitution or laws of

the United States, and thus were outside the scope of Article III. Mayor v.

Cooper, 73 U.S. (6 Wall.) 247, 248 (1868), involved civil claims against the

mayor and alderman of Nashville, Tennessee (who were appointed under the

authority of the President by the then military governor of Tennessee) for trespass

and conversion of chattels occurring during or shortly after the Civil War. The

federally appointed city officials sought removal to federal court; Cooper

opposed, claiming that the removal statute violated Article III of the Constitution. 

Id. at 249. The Court upheld the removal statute’s constitutionality, observing

that averment of one federal defense was sufficient to confer federal jurisdiction,

even if the remainder of the case was premised exclusively on state law. Id. at

252-54. 

Tennessee v. Davis, 100 U.S. at 262, provided the Court with its first

opportunity to consider the constitutionality of removal of state criminal

prosecutions. There, the State of Tennessee prosecuted a federal revenue

collector for murder. The federal officer claimed that “he was assaulted and fired

upon by a number of armed men” while he was in the act of seizing an illegal

distillery, “and that in defence of his life he returned the fire” and killed an

assailant. Id. at 261. As in Cooper, the federal officer sought to remove the
-27-

prosecution to federal court and the State claimed the removal statute was

unconstitutional. In finding that the case “arise[s] under the Constitution or a law

or a treaty of the United States,” the Court examined whether the case turned on

the construction of federal law. Id. at 264. The revenue collector’s defense was

self-defense. The legitimacy of that defense turned on whether the officer had the

authority to seize the distillery—a question of federal law. See id. at 265; Mesa,

489 U.S. at 127-28 (explaining that in Davis, “[p]roof that Davis was not a thief

depended on the federal revenue laws and provided the necessary predicate for

removal”). The early removal statutes at issue in Cooper and Davis were

therefore constitutional because removal was predicated on the existence of a

federal defense. See Mesa, 489 U.S. at 128-29.

In 1948, Congress extended the early, limited removal statutes to cover all

federal officers. See Act of June 25, 1948, ch. 646, 62 Stat. 869, 938 (codified as

amended at 28 U.S.C. § 1442(a)). The new federal officer removal statute

provides, in relevant part:

A civil action or criminal prosecution commenced in a State court

against any of the following may be removed by them to the district

court of the United States for the district and division embracing the

place wherein it is pending:

(1) The United States or any agency thereof or any officer (or

any person acting under that officer) of the United States or of

any agency thereof, sued in an official or individual capacity

for any act under color of such office or on account of any

right, title or authority claimed under any Act of Congress for
-28-

the apprehension or punishment of criminals or the collection

of the revenue.

28 U.S.C. § 1442(a). This statute reflects Congress’s determination that “federal

officers, and indeed the Federal Government itself, require the protection of a

federal forum.” Willingham, 395 U.S. at 407. The Supreme Court has therefore

construed the statute as “not ‘narrow’ or ‘limited’” but rather “broad enough to

cover all cases where federal officers can raise a colorable defense arising out of

their duty to enforce federal law.” Id. at 406-07 (quoting Colorado v. Symes, 286

U.S. 510, 517 (1932)). 

Although the language of the statute seems to permit removal of state

criminal prosecutions whenever a federal officer is sued or prosecuted for an act

under color of his federal office, the Supreme Court has confined the statute to

cases where the officer alleges a colorable federal defense for the act. Mesa, 489

U.S. at 139. Removal is appropriate, for example, where the federal officer

alleges Supremacy Clause immunity as a defense. 

III. Discussion

A. Removal

Wyoming does not dispute that this case involves a federal officer

prosecuted for acts under the color of federal office, nor that Defendants Jimenez

and Livingston have colorable federal defenses based on Supremacy Clause

immunity. The State does argue, however, that removal was procedurally
-29-

improper, in that the district court failed to hold an evidentiary hearing prior to

denying the State’s motion to vacate. The removal statute provides that “[i]f the

United States district court does not order the summary remand of [a criminal]

prosecution, it shall order an evidentiary hearing to be held promptly and after

such hearing shall make such disposition of the prosecution as justice shall

require.” 28 U.S.C. § 1446(c)(5) (emphasis added). The district court concluded

that an evidentiary hearing is not necessary when there is no dispute about the

facts that permit removal. The State argues that this violates the plain text of the

statute, and urges this Court to reverse the decision below and remand to the

district court with instructions to hold the required evidentiary hearing.

The district court’s decision that no evidentiary hearing was required may

seem to be commonsensical. There is no need for a court to hold an evidentiary

hearing in a matter when there are no material facts in dispute. Cf. Scrivner v.

Tansy, 68 F.3d 1234, 1242 (10th Cir. 1995) (“If no facts are disputed [in a habeas

petition] and the issues can be resolved on the basis of the record and the law, no

evidentiary hearing is required.”). But we hesitate to affirm on that ground, both

because the text of § 1446(c)(5) is unequivocal and because, at the time the

district court ordered removal of the state prosecution, it did not yet have the

benefit of any responsive pleading from Wyoming. Section 1442(a)(1) requires a

substantial factual showing to justify removal, and comity demands that federal
-30-

courts dot their i’s and cross their t’s before taking the serious step of removing a

state criminal prosecution to federal court. See Mesa, 489 U.S. at 138 (stressing

the “strong judicial policy against federal interference with state criminal

proceedings”) (internal quotation marks omitted). In order for removal under §

1442(a)(1) to be appropriate, a federal officer (or someone acting under him)

must not only show that he is being prosecuted for the manner in which he carried

out his federal duties, but must also demonstrate that there exists a colorable

federal defense for the act. See id. at 139. There will be cases, like Mesa itself,

when federal officers sued or prosecuted for official acts are not entitled to

removal. Courts must be careful not to remove state criminal prosecutions to

federal court on the basis of “ominous intimations of hostile state prosecutors and

collaborationist state courts interfering with federal officers by charging them

with traffic violations and other crimes for which they would have no federal

defense in immunity or otherwise.” Id. at 138. Removal under § 1442(a)(1) is

not a mere formality. 

In this case the district court ordered removal without giving Wyoming an

opportunity to contest the factual basis for removal. This practice violated the

technical requirements of 28 U.S.C. § 1446(c)(5) and might conceivably have

affected the nature of the inquiry required by § 1442(a)(1). The court had little

before it other than Mr. Jimenez’s motion for removal and the Affidavit of
7As noted above, although Mr. Livingston was a federal contractor rather

than a federal official, the State waived any argument that he is not covered

within the terms of either the removal statute or the doctrine of Supremacy Clause

immunity.

-31-

Probable Cause, on which the Wyoming prosecution was based. The Affidavit of

Probable Cause stated that “a United States Fish and Wildlife employee along

with another person had trespassed on private deeded land in the furtherance of

capturing and/or releasing wolves.” Jimenez App. 20. Although the State’s

apparent admission, in this Affidavit, that the trespass was “in the furtherance of”

the federal policy of wolf capture and release suggests the likelihood of a

Supremacy Clause immunity defense, that admission may not be sufficient,

without more, to establish a colorable federal defense. Consistent with the

language of the Affidavit of Probable cause, it might have been possible, for

example, that Mr. Jimenez’s trespass represented a mere cutting of corners or

carelessness, not reasonably necessary for the wolf capturing operation. We need

not determine whether the district court’s decision to forego an evidentiary

hearing was legal error, however, because we find that any error was without a

doubt harmless. 

We now know that there were no material facts in dispute. It is undisputed

that Defendants Jimenez and Livingston were federal officials,7

 and likewise

undisputed that they have a colorable federal defense. That is all that is required
8Wyoming does not argue that the evidentiary hearing requirement of §

1446(c)(5) is jurisdictional, and it is not. It is well settled that parties may

stipulate to a waiver of the evidentiary hearing, which would not be permitted if

holding the hearing were a jurisdictional requirement. See Long, 837 F.2d at 730. 

-32-

for removal under § 1442(a)(1). In its briefs before this Court, the State has

identified no disputed factual question relevant to removal, and appears concerned

only with the formalities. In our view, to reverse and remand to the district court

for an evidentiary hearing (on nothing), as the State requests, would be a colossal

waste of time and resources.8 

The Defendants-Appellees have not expressly argued that the district

court’s error, if any, was harmless. We may nonetheless address harmless error

sua sponte if three conditions are met: (1) the record is not overly long or

complex; (2) the harmlessness is not debatable; (3) reversal would result in futile

and costly proceedings in the district court. See United States v. Samaniego, 187

F.3d 1222, 1224-25 (10th Cir. 1999). This case satisfies all three requirements:

the record is short, there is no serious doubt about the harmlessness, and a remand

for an evidentiary hearing would be futile. Accordingly, we hold that the failure

to conduct an evidentiary hearing, whether or not error, was harmless. We do

urge district courts when facing a motion for removal under § 1442(a)(1) to

ensure that the State has an adequate opportunity to identify any disputed issues
-33-

of fact relevant to removal, and to conduct an evidentiary hearing to resolve them,

before acting on the motion.

B. Supremacy Clause Immunity

1. Standard of Review

Having established that the district court properly removed the Wyoming

prosecution to federal court, we must now consider whether the district court

properly held that the Defendants are entitled to Supremacy Clause immunity. 

Supremacy Clause immunity dismissals present a mixed question of law and fact

and are reviewed de novo. Tanella, 374 F.3d at 146. The appellate court must

review the evidence in the light most favorable to the non-moving party and

assume the truth of the allegations in the indictment. Id. at 148. However, once a

defendant raises the defense of Supremacy Clause immunity the burden shifts to

the state to supply sufficient evidence to raise a “genuine factual issue” that is

supported by more than mere allegations. See Long, 837 F.2d at 752. The parties

do not dispute these standards, which we believe are appropriate for a review of a

motion to dismiss on Supremacy Clause immunity grounds.

When the district court grants Supremacy Clause immunity on a motion to

dismiss, we review the district court’s decision by asking two questions: (1)

Whether the federal officer had authority for his acts under the Constitution or the

laws of the United States; and (2) whether there is a disputed issue of fact bearing
9We note that denying a motion to dismiss does not foreclose a grant of

Supremacy Clause immunity at a later stage in the litigation. If a court denies a

motion to dismiss because there are genuine issues of fact to resolve, the

resolution of those facts could demonstrate that Supremacy Clause immunity is

appropriate. See, e.g., Johnson, 254 U.S. at 56-57. 

-34-

on whether the federal officer had an objectively reasonable and well-founded

basis to believe that the indicted acts were necessary to carry out his duties.9

2. Federal Authorization

The first question is whether the Defendants had federal authorization for

their acts on February 14, 2004. Mr. Jimenez and Mr. Livingston were acting

under regulations promulgated pursuant to the Endangered Species Act, which

authorizes the designation of nonessential experimental populations of

endangered and threatened species and permits the promulgation of rules

governing the management of these populations. 16 U.S.C. § 1539(j). The gray

wolf was listed as an endangered species in 1978 in the lower 48 states except

Minnesota. Reclassification of the Gray Wolf in the United States and Mexico,

with Determination of Critical Habitat in Michigan and Minnesota, 43 Fed. Reg.

9607 (Mar. 9, 1978). In 1994, the Secretary of the Interior adopted a gray wolf

recovery program that provided for the annual reintroduction of fifteen wolves in

Yellowstone National Park and central Idaho. Wyo. Farm Bureau Fed’n v.

Babbitt, 199 F.3d 1224, 1228-29 (10th Cir. 2000). The Department of the Interior

published final rules authorizing the USFWS to manage gray wolf populations in
10Since the acts at issue in this prosecution, the Department of the Interior

has updated the gray wolf regulations. See 70 Fed. Reg. 1286-01 (Jan. 6, 2005). 

We focus on the regulations in effect at the time of the relevant acts.

-35-

the Yellowstone Management Area. 50 C.F.R. § 17.84(i)(7)(ii).10 The regulations

designate all of Wyoming, as well as parts of Idaho and Montana, as the

boundaries of the nonessential experimental population area for the Yellowstone

Management Area. Id. The final regulations are intended to give the

reintroduced gray wolves an opportunity to thrive while at the same time mitigate

the concerns of ranchers about livestock predation. For example, ranchers may

take nonlethal measures to harass wolves on their property, id. § 17.84(i)(3)(i),

and may kill wolves that are actively attacking their livestock, id. §

17.84(i)(3)(ii). 

The regulations do not merely authorize, but impose an obligation on the

USFWS to monitor wolves. Id. §17.84(i)(8) (“The reintroduced wolves will be

monitored during the life of the project . . . .”). This monitoring regulation is

important because it provides direct federal authorization for the actions of the

Defendants. 

We note, however, that the regulation does not contain an explicit grant of

authority for USFWS staff to trespass. The regulations that do address private

land do not state whether USFWS officials need to secure permission from

landowners before operating on their land. For example, in a section addressing
-36-

problem wolves that have attacked livestock, USFWS staff have the authority to

relocate “[a]ll wolves on private land” to “other areas within the experimental

population area if continued depredation occurs.” Id. § 17.84(i)(3)(vii). The lack

of any reference to the permission of the land owner distinguishes these

regulations from those governing the reintroduction of other species. For

example, the Mexican gray wolf regulations state: “If any wolves move onto

private land outside the designated recovery area(s), but within the Mexican Wolf

Experimental Population Area, the Service or an authorized agency will develop

management actions in cooperation with the landowner including capture and

removal of the wolf or wolves if requested by the landowner.” Id. § 17.84(k)(11). 

We are hesitant to read too much into the differences between this language and

the gray wolf regulations, but there is a plausible inference that USFWS staff

acting pursuant to the gray wolf regulations have a slightly freer hand when

working on private land than those acting pursuant to the Mexican wolf

regulations. 

In any event, Supremacy Clause immunity does not require that federal law

explicitly authorize a violation of state law. The Supreme Court found federal

authorization in Neagle despite the fact that the Attorney General’s order did not

explicitly authorize the use of lethal force, and in Thomas even though the federal

oleomargarine provision did not authorize violation of Ohio’s notice requirement. 
-37-

The question is not whether federal law expressly authorizes violation of state

law, but whether the federal official’s conduct was reasonably necessary for the

performance of his duties. Accordingly, there is no question that the Defendants

had federal authorization for the capture and collar operation that led to their

indictments.

3. Reasonable and Necessary

Having determined that the Defendants had federal authorization for their

conduct, we next ask whether Mr. Jimenez and Mr. Livingston had an objectively

reasonable and well-founded basis to believe that their actions were necessary to

carry out their duties. Because the State does not dispute that the federal agents

subjectively believed their actions were necessary, we consider only whether that

belief was well-founded and objectively reasonable. As mentioned earlier, we

decline to consider whether subjective reasonableness is a necessary consideration

in Supremacy Clause immunity cases.

It is undisputed that tracking the Washakie pack was a difficult enterprise.

Extensive forest cover and frequent windy conditions in the home range of the

wolves make it difficult for the USFWS to attend to the duty to monitor the

wolves on their own turf. It is also uncontested that the spotting of the pack far

outside of its normal range on February 13, 2004, presented unusually favorable

conditions for the Defendants to capture and collar the wolves. Given the
11 Under Wyoming law, unauthorized presence on private land constitutes

criminal trespass only when the defendant enters or remains “knowing he is not

authorized to do so, or after being notified to depart or to not trespass.” Wyo.

Stat. § 6-3-303(a). On the facts of this case, therefore, the Defendants would

seem to have a plausible defense under state law. The question for purposes of

Supremacy Clause immunity, however, is not whether the federal official is guilty

under state law, but whether he has established immunity under federal law. 

Neagle, 135 U.S. at 54. It is logically possible for an indicted federal official not

to be immune, but to be not guilty. 

-38-

difficulty of tracking the wolves there is no question that it was objectively

reasonable for the Defendants to believe that taking advantage of this opportunity

was necessary to carry out their duty to monitor the wolves.

The more difficult question is the reasonableness of their decision to

immobilize the wolves and place them on land that might turn out to be private. 

The Defendants do not argue that federal law gives them a right to trespass with

impunity when pursuing wolves, nor do they argue that when exigent

circumstances exist there is a limited right to trespass. Thus, we need not

consider those arguments. The record, including declarations from cattle ranchers

hostile to the wolf program, shows that Mr. Jimenez is conscientious about

securing permission from land owners when he knows he might be on their land.

Rather, the Defendants argue that they made reasonable attempts to determine

whether they were on private land in this case and that there were no indications,

such as signage or fences, that they were on private land.11 Thus, the Defendants

contend, there were objective reasons to believe that they were not on private
-39-

land. See Texas v. Carley, 885 F. Supp. 940, 945-46 (W.D. Tex 1994) (granting a

motion to dismiss on Supremacy Clause immunity grounds to a USFWS employee

indicted for trespass, where the officer had no indication that the land was

private). It is not clear to us that the Defendants would have lacked an

objectively reasonable basis to believe their actions were necessary to the

performance of their functions, even if they had been aware they were on private

land. But their claim of immunity is based on that lack of awareness, and we

therefore address the issues in those terms. 

Wyoming counters that there were signs in the area and that the GPS

coordinates from the helicopter indicated that each discharge of a dart or net was

over private land. Wyoming argues that this evidence was sufficient to create a

question of fact as to whether the Defendants’ belief that they were on public land

was objectively reasonable. 

We believe the undisputed evidence in the record establishes that the

Defendants’ belief that they were on private land was objectively reasonable and

well-founded. Given the expansive range of gray wolves as well as their

propensity to run in any direction after being darted, it would be an onerous

burden on federal officers like Mr. Jimenez to require them to determine the

precise boundaries of land that might be encountered, on threat of criminal

prosecution if they should be in error. Cf. Davis, 100 U.S. at 263 (warning that
-40-

state interference with federal law may “paralyze the operations of the

government”). The undisputed evidence shows that the area in which this wolf

collaring operation took place is a jumble of federal, state, and private land. Mr.

Jimenez consulted both the fixed-wing pilot and the helicopter pilot in advance of

the operation and secured their opinion that the operation would take place on

public land. It is likewise undisputed that the location where Mr. Jimenez

processed the wolves was close to a county road, and that it took the specialized

skills of state surveyors to determine that the operation extended beyond the

county right-of-way for the road. There were neither fences nor signs between

the road and the processing location, though there were some signs in the

distance. Moreover, when Mr. Kruger, a part owner and employee of the Larsen

Ranch, came by he chatted amicably with Mr. Jimenez and offered no indication

that Mr. Jimenez and Mr. Livingston were trespassing on Ranch property. 

Wyoming law treats the presence of a person on the private land of another

as criminal trespass only when he enters or remains “knowing he is not authorized

to do so, or after being notified to depart or to not trespass.” Wyo. Stat. §

6-3-303(a). Notice may be provided in two ways: “(i) Personal communication to

the person by the owner or occupant, or his agent, or by a peace officer; or (ii)

Posting of signs reasonably likely to come to the attention of intruders.” Id. A

reasonable person operating on what might be private land in the State of
-41-

Wyoming would presumably be on alert for these two types of notice, and would

interpret their absence as an indication he was not trespassing. In particular, the

Defendants’ encounter with Mr. Kruger would induce reasonable persons to

believe either that they were not on Ranch property or that he acquiesced to their

presence. 

The State argues that there are some uncontested facts that suggest that the

Defendants should have known they were on private land. For example, the

parties do not contest that when one of the Defendants fired a dart or net from the

helicopter, the pilot would press a button to lock in the GPS coordinates at the

time. The parties also do not dispute that comparing these coordinates to a

detailed map of the area shows that each time the pilot locked in coordinates the

helicopter was over private land. Wyoming asserts that this information creates

an issue of genuine fact as to whether the officers were objectively justified in

their belief that they were operating on public land. We disagree. Supremacy

Clause immunity cases require courts to evaluate the circumstances as they appear

to federal officers at the time of the act in question, rather than the more subtle

and detailed facts later presented to a court. See Neagle, 135 U.S. at 76. At the

time the pilot locked in the coordinates, the Defendants were manning a net gun

and dart gun on a helicopter that had no doors. These circumstances made

consulting a map difficult, if not impossible. At most, the GPS coordinates could
-42-

have enabled the Defendants, after the fact, to determine where they had been

when they encountered the wolves, but this could not have provided information

regarding land ownership during real time. Moreover, the GPS coordinates are

thin evidence of trespass because the helicopter did not land at these points and

the wolves did not immediately go down after being hit. Even if objective

reasonableness required on-the-fly cross-referencing of the GPS data with map

data, which we do not believe it does, the GPS data would only demonstrate that

the helicopter stage of the operations took place over, but not on, private land. 

Wyoming also argues that the district court ignored evidence submitted

about the signage and structures in the area where Mr. Kruger encountered the

Defendants. Wyoming contends that these indications could have alerted the

Defendants that they were on private land, creating a disputed factual question. 

There are two flaws in this argument. First, it is uncontested that the structures

were not in the immediate vicinity of the Defendants while they were tending to

the wolves. Structures and fences in the distance suggest only that the area off in

the distance is private land and say little about the area where the Defendants

were dealing with the wolves. Indeed, the presence of far-off structures and

fences may reenforce the impression that an unfenced, unsigned area adjoining a

public road is not private. We find it significant that the County had to hire

professional surveyors to determine whether the Defendants were on a public
-43-

right of way or on deeded private land. Objective reasonableness does not require

federal actors carrying out their duties to estimate property boundaries with a

surveyor’s precision, at the peril of criminal prosecution. 

Second, even on the assumption that the Defendants saw or should have

seen the signs identified by Wyoming, these did not provide the Defendants

reason to know they were trespassing, because the signs implicitly authorize

entry. The signs contain admonitions such as: “Hunter Management Area Ends

Here—Respect the Landowner and the Land,” “Notice: No Off Road Vehicle

Travel,” “Walk-In Area. Foot Traffic Only [Except on Designated

Trails]—Hunting on this land is provided for your enjoyment—Respect the

Landowner And the Land,” and more cryptically “No Traffic Allowed Off Lease

Roads Without Permission of Landowner.” Jimenez App. 174, 176, 178. It is

reasonable to read these signs as permitting members of the public to enter the

private land, and even hunt animals on that land, so long as they respect the land

and do not drive vehicles off road. If the Defendants did see these signs they

would have reason to believe the signs indicated private land, but they would also

have reason to believe that their presence on private land was permitted. Thus, it

does not matter whether the Defendants actually saw the signs. In either case

they would have a well-founded basis to believe that they were not committing
12 The only material distinction between the conduct of Mr. Jimenez and the

conduct of Mr. Livingston was Mr. Jimenez’s hike of roughly a quarter mile to

retrieve a darted wolf. Wyoming has not argued that this foray differed in any

material way from the rest of the Defendants’ activities that day.

-44-

criminal trespass, and thus that their entry on the land was an objectively

reasonable mode of carrying out their federal duties.

Our review of the evidence presented to the district court demonstrates that

while the Defendants were attempting to fulfill their federal duty to monitor the

wolves through a capture and collar operation they confined their acts to an

objectively reasonable view of the scope of their authority. Thus, the district

court correctly granted immunity to the Defendants and correctly dismissed the

indictment.12

IV. Conclusion

Granting immunity in this case serves the purposes for which Supremacy

Clause immunity was developed. The record evidence supports the suspicion that

the prosecution of Mr. Jimenez and Mr. Livingston was not a bona fide effort to

punish a violation of Wyoming trespass law, which requires knowledge on the

part of a trespasser, see Wyo. Stat. § 6-3-303(a), but rather an attempt to hinder a

locally unpopular federal program. An early grant of immunity reduces the risk

that the possibility of state criminal prosecution will deter the performance by

federal officers of their federal duties. For the reasons stated above, we
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AFFIRM the order of the district court denying Wyoming’s motion to vacate

removal and granting the Defendants’ motion to dismiss.