OPINION
Efrаin Beeerra-Garcia challenges the district court’s denial of his motion to suppress evidence, namely the discovery by tribal rangers of illegal aliens in his van while crossing the Tohono O’odham Nation. Although the scope of the rangers’ authority and the location of the stop on reservation land inform our analysis, this case boils down to a determination whether the rangers’ stop of Beeerra-Garcia was reasonable. We conclude that it was and thus affirm.
Background
The setting of this case is the Tohono O’odham Indian Reservation, which covers a sprawling 90 miles across southern Arizona. The Tohono O’odham Police Department includes a division of tribal rangers, officers who have less power than fully-authorized tribal police officers. The rangers are authorized to patrоl the reservation and report suspicious activity to tribal police officers or the United States Border Patrol. According to the testimony of two rangers and a tribal police officer, rangers do not have authority to stop suspicious vehicles. Vehicles that stop voluntarily may be detained until the arrival *1170 of officials who have authority to arrest. If a suspicious vehicle does not voluntarily stop and instead exits tribal land, the rangers must let the car go. A ranger may make an arrest at the direction of a tribal police officer. Thus, the rangers’ primary duties are to patrol, looking for suspicious activity, to report to the police department and other authorities (usually the Border Patrol), and to detain suspects who voluntarily stop.
Tribal Rangers Andrew Ruiz and Denvеr Calabaza were patrolling on a remote dirt road on the reservation when they saw a van heading north. They were about twenty miles from the nearest highway and three miles from the nearest village, Queens Wells. The tribal police department had, in the preceding weeks, received complaints of unidentified vehicles driving through the area. Because trespassing is a significant problem and only local ranchers typically use the roads in this vicinity, the rangers make a practice of calling in the license plate numbers for all unknown vehicles transiting that area. The rangers did not recognize the van, which did not have a reservation license plate, and, in keeping with their standard practice, they followed it in order to report the license plate number. When the rаngers turned on their emergency hazard lights, the van stopped.
Almost immediately after the van stopped, the driver, Becerra-Garcia, got out and walked toward the rangers, leaving the van door open. Both of the rangers had already stepped out of their jeep. Ranger Calabaza asked Becerra-Garcia for identification to determine whether he was trespassing, but Becerra-Garcia did not speak English. Ranger Calabaza tried asking in Spanish. In response, Becerra-Garcia motioned toward the van, and Ranger Calabaza went to the van to retrieve Becerra-Garcia’s identification. As Ranger Calabaza approached the van, he saw through the open door more than twenty undocumented aliens stuffed inside.
The rangers called the Tohono O’odham Police Department, and the police contacted the U.S. Border Patrol. At the direction of the police department, the rangers detained Becerra-Garcia and put him in the back seat of their jeep until the Border Patrol and tribal police officers arrived about thirty minutes later.
Becerra-Garcia was later charged with conspiring to transрort illegal aliens and with transporting illegal aliens in violation of 8 U.S.C. § 1324(a)(l)(A)(ii). The district court denied Becerra-Garcia’s motion to suppress the evidence of the illegal aliens. Becerra-Garcia then entered a conditional plea of guilty, preserving his right to appeal the denial of his motion to suppress.
DisCussion
We review de novo a district court’s denial of a motion to suppress.
United States v. Garcia,
At issue in this appeal is the intersection of a tribal policy and the Fourth Amendment in the context of a motion to suppress evidence stemming from a traffic stop. Ironically, the parties each argue thаt the Fourth Amendment does not apply. Even more ironically, both are correct, but not for the reasons they offer.
Becerra-Garcia claims that the tribal officers were acting in a private capacity and therefore state law on citizen’s arrest, not the Fourth Amendment, comes into play. *1171 The Government counters that Becerra-Garcia stopped voluntarily and thus there is no Fourth Amendment unreasonable seizure consideration. Both are wrong. The tribal officers were government agents, not private actors, and the stop was not voluntary. Yet the Fourth Amendment does not apply because the constitution does not directly apply to the conduct of tribal governments. Even so, a federal statute imposes precisely the same constraints оn tribal governments as the Fourth Amendment, so Fourth Amendment law comes into play.
I. The Applicable Law
At the outset, this case presents a thorny issue because the stop was made by tribal rangers on tribal land, although the arrest was made by federal officers. The wrinkle is that, while both parties have briefed this appeal as a Fourth Amendment case, the Fourth Amendment does not directly govern the conduct of tribal governments.
United States v. Manuel,
We assume, as have courts before us, that suppression of evidеnce in a federal proceeding would be appropriate if the rangers’ conduct violated ICRA.
See United States v. Male Juvenile,
Becerra-Garcia would have us avoid analyzing this appeal through the Fourth Amendment lens, not because the rangers are tribal officers, but because they acted in their capacity as private citizens. Becerra-Garcia suggests that, because the tribal rangers lack the authority to stop cars, they were not acting in their capacity as government аctors. Instead, he argues that citizen’s arrest law, not the Fourth Amendment, controls the analysis.
See State v. Chavez,
*1172
This approach, while creative, misses the mark. For Fourth Amendment purposes, an individual is a government agent if the government knew of and acquiesced in the officer’s activities, and the party performing a seizure intended to assist law enforcement and did not act to further his own ends.
United States v. Reed,
n. The Stop — A Seizure Under Fourth Amendment Standards
The threshold question is whether there was a stop by the rangers or whether Becerra-Garcia voluntarily stopped his van. The government takes the position that the Fourth Amendment is not implicated because Becerra-Garcia stopped his van voluntarily, not as a result of government intrusion.
Becerra-Gаrcia testified that he stopped because the rangers flashed their emergency lights whereas the rangers claimed that they activated their lights only after the van had stopped. The district court weighed this conflicting testimony and sided with Becerra-Garcia, finding that the rangers effected a stop of the van.
We review the district court’s factual findings for clear error, and we do not disturb those findings unlеss “they are without foundation.”
United States v. Diaz-Cardenas,
hi. Reasonableness Of The Stop Under Fourth Amendment Standards
The district court held that the rangеrs’ suspicion of trespassing upon the Indian Nation justified the stop. Following the stop, the rangers detained Becerra-Garcia, conduct that fell squarely within their authority, and the Border Patrol made the actual arrest. Becerra-Garcia does not contest the finding with respect to reasonable suspicion. The sole argument he offers for why the stop was unreasonable is that the rаngers lacked authority under tribal law to effectuate the stop.
Before we address Beeerra-Garcia’s argument, we take a detour to examine the authority of the Tohono O’odham rangers. Becerra-Garcia has not offered proof of any statute or regulation that circumscribes the rangers’ powers. Instead, Be-cerra-Garcia relies entirely on testimony that thе rangers had been told they lacked *1173 authority to stop vehicles. The source of this directive — whether statute, rule, fiat, or policy — was never explored. Despite the murkiness surrounding the scope and source of the rangers’ powers, the evidence that the rangers lacked authority to stop drivers was uncontested. Consequently, for the purposes of this opinion, we assume that although the rangers had authority to detain individuals on the reservation, they were not authorized to stop Becerra-Garcia. We also consider the source of the limits on the rangers’ authority — whatever it may be — to be the equivalent of tribal law. But, as we discuss below, the rangers’ authority under tribal law is not the linchpin for determining the admissibility of the evidence obtained as a result of the stop.
A. FRAMEWORK FOR ANALYSIS — FEDERAL Law Governs Thе Reasonableness Of The Seizure
We start with the proposition that”[t]he general rule ... is that evidence will only be excluded in federal court when it violates federal protections, such as those contained in the Fourth Amendment, and not in cases where it is tainted solely under state law.”
United States v. Cormier,
For many years, we left unresolved the question whether state or federal law governed the reasonableness of seizurеs,
see, e.g., United States v. Clawson,
In the oft-cited case of
United States v. Chavez-Vernaza,
We note that the question of whether and how state law affects the constitutional reasonableness of a seizure has long troubled courts and has produced inconsistent results.
See Santoni v. Potter,
The weight of authority establishes that the test of whether a search or seizure violates the Fourth Amendment “is one of federal law, neither enlarged by what one state court may have countenanced, nor diminished by what another may have colоrably suppressed.”
Elkins v. United States,
b. The Seizure Was ReasoNable
Having established that, in this ease, the legality of the seizure does not depend on the rangers’ authority under tribal law, we turn to the question whether, under Fourth Amendment standards, the stop was reasonable. “The Fourth Amendment requires only reasonable suspicion in the context of investigative traffic stops.”
Haynie v. County of Los Angeles,
Becerra-Garcia urges us to hold otherwise, suggesting that we adopt what, at bottom, is a bright-line rule for determining reasonableness: that a stop is automatically unreasonable if the officers lacked authority to conduct the seizure. The difficulty with this argument is that it seeks, in effect, to undo the general principle that federal law, not state or tribal law, governs the inquiry.
The reasonableness of a seizure is generally analyzed on a case-by-case basis, not according to bright-line rules.
See, e.g., Terry v. Ohio,
Our holding is consistent with our general recognition that Indian tribes are sovereigns with the power to enforce internal laws.
See, e.g., United States v. Enas,
AFFIRMED.
Notes
. The Indian Civil Rights Act (ICRA) provides that "No Indian tribe in exercising powers of self-government shall ... violate the right of the people to be secure in their persons, houses, papers, and effects against unreasonable search and seizures.” 25 U.S.C. § 1302(2).
. We acknowledge that in the civil context, habeas corpus relief generally is the sole federal remedy for a violation of ICRA.
See Santa Clara Pueblo v. Martinez,
. We have not deemed state law wholly irrelevant to Fourth Amendment analysis. Our precedent supports at least two exceptions to the principle that compliance with state law does not determine constitutional reasonableness, searches incident to arrest and inventory searches.
See Cormier, 220
F.3d at 1111—12 (reasonableness of search incident to arrest depends on legality of arrest under state law and reasonableness of inventory search depends on compliance with state and local procedures). The stop of Becerra-Garcia does not fall under either of these exceptions, nor does the federal test for its validity incorporate state or tribal law. Bеcerra-Garcia was the subject of an investigatory traffic stop, the reasonableness of which depends only on reasonable suspicion, not on compliance with state or tribal law.
See Haynie v. County of Los Angeles,
. We acknowledge some inconsistency in our cases on this broad issue.
See, e.g., Bingham v. City of Manhattan Beach,
