Flashpoints of State-Federal Cooperation in Immigration Enforcement: Part III—Traffic Stops in the Deportation Pipeline

Previous parts of this series on state involvement with federal immigration enforcement examined so-called “sanctuary jurisdictions,” arrest authority, and detention space.  This final piece dives into the legal implications of what is likely the most widespread and intrusive manifestation of immigration enforcement: the traffic stop. Due to the ambiguous justifications for some of these stops, the resulting legal issues raise particular concerns regarding potential racial profiling and how law enforcement interacts with their local communities.

Montana Traffic Stops

Even in the absence of formal agreements, limited available information suggests that informal cooperation, particularly information-sharing, is commonplace between local authorities and federal immigration enforcement—sometimes to the consternation of the local community.[1]

In 2025, local law enforcement from Helena, Montana was engaged in a joint operation with ICE in an effort to arrest one man — Anderson DeJesus Bastidas Linares —under criminal warrant, but instead followed and pulled over another man—Martinez Marvan—driving through the targeted area.  Though officers determined that Marvan was not the targeted individual, federal agents concluded he was removeable, and Marvan was, according to bystanders, “taken by people in vests” into an unmarked vehicle, and then, apparently, to a county detention center (notwithstanding the lack of any 287(g) agreement, discussed in a previous segment, that would have granted legal authority to do so).  The incident sparked community outrage, involving allegations of racial profiling, and that detention center officials prohibited Marvan from speaking with his attorneys before he was transferred out of the center.

Also in 2025, the Great Falls Police Department called ICE to the scene of a “suspected trespassing” (an offense well outside ICE’s enforcement prerogative). Upon arrival, ICE stopped someone—Duran Valdivias—who was not suspected of trespassing.  Valdivias was found to be without lawful status and arrested. Local law enforcement stated that it notifies federal immigration authorities if they suspect enforcement is necessary, emphasizing that “ICE has always been in a good relationship with local law enforcement.”

Both of these incidents have raised concerns that Montana’s local law enforcement is trying to assist federal immigration enforcement efforts by targeting individuals based on apparent ethnicity.

HB 278 & Racial Profiling

Montana law enforcement’s willingness to call federal immigration authorities to the scene to question individuals of minority ethnic groups appears to be at least partially fueled by a 2025 Montana law, HB 278.  This law allows police to extend a traffic stop to attempt to determine immigration status if the officer has reasonable suspicion that the individual might be undocumented, and directs officers to notify ICE.  

One group, Valley Neighbors of the Flathead, filed a lawsuit in state court challenging the statute’s constitutionality, alleging that the Whitefish Police Department and Montana Highway Patrol had on several occasions engaged in racial profiling in pulling individuals over and calling federal immigration authorities to the scene.  The court threw the case out, concluding that Valley Neighbors had not shown that its members were directly impacted by the law sufficient to be able to challenge it.

The court left the door open, however, for the matter to be revived by someone who is more directly affected by the law.  Should this occur, the court will have several interesting constitutional questions to answer.  The first is whether, as Valley Neighbors alleges, the Montana Constitution requires “particularized reasonable suspicion” instead of just “reasonable suspicion” to extend a traffic stop.  The extra word does not seem to have had much analysis in Montana caselaw thus far[2], but it might play a role here where, racial profiling is alleged. Besides race or language, an officer in the midst of a traffic stop is unlikely to have much else to go off of in concluding that the individual at the wheel might be undocumented.  

The mass deportation efforts being effectuated at the federal level raise similar profiling concerns, as the careful pre-arrest research, intended to ensure that the targeted individual is in fact removeable, is replaced with ad-hoc arrest efforts. Notably, the United States Supreme Court seemingly gave the nod to these practices in a so-called “shadow docket” ruling overturning a lower court stay on certain Trump Administration enforcement efforts.  Though the order was not accompanied by a majority opinion, Justice Kavanaugh wrote a concurrence stating that “apparent ethnicity” could be a “relevant factor” capable of supporting an immigration traffic stop, if supported by other factors (including items like type of employment and language).[3]

The “Reverse Silver Platter Doctrine”

While federal-local immigration cooperation debates typically involve local authorities helping federal immigration agents, the inverse scenario also sometimes arises. 

Courts, generally speaking, refuse to admit evidence in criminal proceedings that police discovered by violating the defendant’s Fourth Amendment right to be free from unreasonable search and seizure.  This incentivizes police to abide by the Constitution, rather than risk the case being dismissed for lack of admissible evidence.  

Historically, the Fourth Amendment applied only to federal authorities, while state and local law enforcement were free to disregard such rights.  When federal agents would encourage their local law enforcement colleagues to conduct searches that the federal agents were themselves prohibited from conducting, local law enforcement would then present the resulting evidence to the federal agents on a “silver platter” as a way to try to skirt the Fourth Amendment.

State and local law enforcement are subject to the Fourth Amendment[4] in the modern era, and, now, the situation is reversed.  Some states, like Vermont and Montana, have additional heightened state constitutional constraints.  Meanwhile, federal border patrol agents operating near the border are subject to relaxed Fourth Amendment standards. A border patrol agent might thereby be able to conduct a stop or search that would have been illegal (and the resulting evidence deemed inadmissible) had the officer been a state police officer.  Thus, when border patrol officers discover—using means considered unlawful under the state constitution—evidence useful for state criminal proceedings, they may present it to their local counterparts on what has been termed a “reverse silver platter.”  

The question some state courts have had to face, therefore, is whether to accept evidence gathered by federal border patrol agents using methods that would have been illegal if done by a local officer subject to the heightened state constitution. The New Mexico Supreme Court determined the answer was no.[5]  Historically, the Vermont Supreme Court had seemingly reached the opposite conclusion, accepting evidence collected by border patrol agents using means that would violate the state constitution.[6]

But in 2021, the Vermont high court changed tack.  In State v. Walker-Brazie, 280 A.3d 24 (Vt. 2021), a federal “roving patrol,”—i.e., agents driving within the U.S., rather than located at a stationary checkpoint or border crossing—conducted a traffic stop that did not comport with the Vermont Constitution’s heightened privacy requirements. The Border Patrol agents did not find an immigration violation, but they did discovery drug evidence that was turned over to local law enforcement for a state criminal prosecution. 

As a law student clinician, I helped draft an amicus brief in that case arguing that the drug evidence should be rejected by the state criminal court, just as it would have been if the search was conducted by state police. Ultimately, the Vermont Supreme Court agreed, deeming the drug evidence inadmissible.  However, in reaching this result, the Court distinguished evidence gathered by a “roving patrol” from that discovered by agents at a fixed checkpoint or border crossing, which it had previously green-lighted. The basis of the distinction between roving patrols and checkpoints is thin, and likely reflects the Court’s compromise effort to back away from entanglement with federal immigration enforcement without overruling precedent.  

Ultimately, excluding such evidence from state courts will likely do little to deter federal authorities from impinging upon state privacy rights while pursuing their own immigration purposes.  Instead, rulings like those in Vermont and New Mexico reflect a principled desire for judiciaries to stand with the constitutional rights of their residents rather than become enmeshed in what many see as increasingly repugnant tactics of federal immigration enforcement.[7]  As the federal government’s immigration crackdown continues, more state judiciaries—including Montana’s, which presides over an immense northern international border—will likely be called upon to wrestle with this issue. 

Conclusion

In electing President Trump for a second term, the public endorsed a significant change in immigration enforcement.  As the consequences of the Administration’s crackdown have been revealed, the public may be having second thoughts.  Regardless, numerous local and state-wide jurisdictions will continue to have to grapple with the role they wish to play in this unfolding drama, and the many moral and legal hazards it presents. 

[1]  See Ben Levey, Disrupting the Jail-to-Deportation Pipeline in Wisconsin, 2023 Wis. L. Rev. 2027, 2037 (2023) (describing financial incentives underlying Wisconsin counties’ information sharing with ICE); Matt Hudson, Local Immigration Enforcement System Working, Officials Say (Mar. 3, 2025) https://montanafreepress.org/2025/03/03/local-immigration-enforcement-system-working-officials-say/ (Cascade County Sheriff and Great Falls Police Chief relating that their “people work well with local ICE agents”).  House Bill 439, would have required federal immigration authorities keep local law enforcement abreast of their planned efforts.  Id.  This bill, in addition to obvious Supremacy Clause problems under the U.S. constitution, failed to pass.

[2] See State v. Hoover, 2017 MT 236, ¶ 19 (apparently indicating that an officer may “articulate[] a reasonable suspicion that an illegal break-in might possibly be in progress” without necessarily having “an objectively reasonable, particularized suspicion of criminal activity”).

[3] Noem v. Vasquez Perdomo, No. 25A169, 2025 WL 2585637, at *1 (U.S. Sept. 8, 2025) (Kavanaugh J., concurring). Justice Sotomayor dissented: “We should not have to live in a country where the Government can seize anyone who looks Latino, speaks Spanish, and appears to work a low wage job.” Id. at *6 (Sotomayor, J., dissenting).

[4] Elkins v. United States, 364 U.S. 206, 215 (1960).

[5] State v. Cardenas-Alvarez, 25 P.3d 225, 232 (N.M. 2001).

[6] State v. Coburn, 683 A.2d 1343 (Vt. 1996)

[7] Walker-Brazie, 280 A.3d at 35-36 (“The intrusion into defendants’ privacy was not somehow lessened because the search was conducted by a federal agent.”); Cardenas-Alvarez, 25 P.3d 225 (New Mexico court did “not claim the authority to constrain the activities of federal” agents, but “would not abandon [its] guard of those [constitutional] protections in order to accommodate evidence thereby yielded”).