Flashpoints of State-Federal Cooperation in Immigration Enforcement: Montana and Elsewhere—Part I: Sanctuary Jurisdictions
(first published June 5, 2026 at https://andersnewbury.substack.com)
“[F]ederalism secures to citizens the liberties that derive from the diffusion of sovereign power. . . . By denying any one government complete jurisdiction over all the concerns of public life, federalism protects the liberty of the individual from arbitrary power.”
--- Bond v. United States, 564 U.S. 211, 220–22 (2011).
Background:
The interplay between the authority of the sovereign states and the federal government lies at the core of the American democracy. That tension has been the subject of numerous legal battles over the centuries, and continues to play a central role in one of the most pressing policy issues of the day: immigration enforcement.
As early as 2010, the Research and Development (RAND) Corporation pointed to the mismatch between federal immigration enforcement resources and the number of individuals living in the U.S. without legal status, concluding “that it is utterly unrealistic to expect that the immigration problem can be solved by federal law enforcement alone.” [1] The RAND Corporation recommending that the army of local law enforcement agents (LLEAs) operating within the country might be enlisted to assist in the project. The Obama Administration put the recommendation into action, forging numerous cooperative measures with state and local law enforcement, setting records for deportations and earning that President the moniker “deporter-in-chief” among migrant advocates.[2] In his first term, President Trump’s controversial approach engendered local resistance, and his inability to marshal consistent support from local law enforcement across the political spectrum contributed to his inability to match his predecessor in deportation efforts.[3]
Trump 2.0 has raised the stakes on the immigration debate, returning to office in large part due to the interim administration’s border security failures and promising the largest mass deportation in history. Again, the extraordinarily controversial nature of the Administration’s tactics has corresponded with difficulty enlisting the help of local law enforcement in the politically-unaligned jurisdictions where many undocumented residents are located. And yet again, the administration is falling short of its stated goals.[4]
As a result, the Trump administration has resorted to offering to pay individuals to “self-deport,” imposing harsh conditions of detention upon those who challenge the legality of their deportation,[5] threatening state and local jurisdictions that decline to assist enforcement efforts,[6] and expanding the enforcement net well beyond the very small subset[7] of the undocumented population believed to be dangerous.[8]Meanwhile, the Administration’s aggressive mandates and massive expenditures have swelled the ranks of federal immigration enforcement with inexperienced—sometimes poorly vetted—new recruits.[9]
Local involvement is among the more controversial aspects of immigration enforcement, as residents see their own local law enforcement expending finite resources aiding a federal immigration crackdown many see as heartless.[10] Even in Montana—a state that voted overwhelmingly for Trump—local-federal cooperation on immigration enforcement has been a flashpoint, and courts are being asked to weigh in on the tangled federalism questions raised by these efforts.
In 2020, I authored both a law review article and part of an amicus brief (in collaboration with Vermont Law School’s Appellate Clinic) addressing state-federal cooperation on immigration enforcement. With local involvement with federal immigration authorities once again a point of interest, this piece summarizes the relevant law surrounding various forms of local-federal immigration enforcement cooperation in Montana and elsewhere.
Commandeering Local Resources: “Sanctuary Jurisdictions”
The current Trump Administration has shown an unprecedented willingness to use state power to coerce compliance with the President’s political and personal aims. One example is the Administration’s 2025 creation of a list of “sanctuary jurisdictions” singled out for threats of withholdal of federal funds (and, seemingly, targeting for increased federal law enforcement or military presence).[11]
The term “sanctuary jurisdiction”—which predates the Trump administration—is neither legally meaningful nor an accurate descriptor. The U.S. Supreme Court held in Arizona v. United States[12] that immigration enforcement is the federal government’s prerogative, rejecting J. Scalia’s dissenting argument that state governments had inherent immigration enforcement authority. Nevertheless, law enforcement agencies across local, state, and federal agencies often, to varying degrees of formality, enjoy close cooperative working relationships with one another.[13] As federal deportation efforts have become more controversial, some states and cities have decided to limit their own law enforcement’s availability to assist with federal immigration enforcement.
As a legal matter, these jurisdictions are not “sanctuaries.” Under the U.S. Constitution’s Supremacy Clause, governors and mayors are powerless to stop federal immigration enforcement activities in order to protect their undocumented population. Instead, they are simply jurisdictions that have declined to volunteer their own resources to the (federal) cause.
According to the Trump Administration, however, any jurisdiction to have enacted policies to refuse to volunteer their own information, jail access, funding, or detainer compliance (to be discussed in more detail later) to federal immigration officers might be singled out for funding cuts as a “sanctuary” jurisdiction. These arm-twisting efforts have seen mixed results: the Democratic mayor of Louisville folded to the Trump Administration’s threats; in contrast, the Republican governor of Vermont has continued to oppose state resources being used to assist with deportation efforts.[14]After ICE conducted a multi-day series of raids in Connecticut, in which it claimed to be responding to Connecticut’s “sanctuary” status, Gov. Ned Lamont told U.S. Attorney General Pam Bondi that Connecticut would not amend its immigration policies, despite threats to funding.[15]
As courts have made clear, state and local assistance with immigration enforcement, generally, is purely voluntary, as the states-rights provision of the Tenth Amendment forbids the federal government from “commandeering” state resources.[16] So far, at least two federal judges have rejected the Trump Administration’s effort to enforce its “sanctuary jurisdiction” policy against states.[17]
Though the “sanctuary” moniker adds little to any meaningful legal debate, real battles have and continue to arise in the context of traffic stops, arrests, detentions, information sharing, and more obscure forms of state-federal overlap. These flashpoints will be examined in more detail in later installments of this series on state-federal immigration enforcement debates.
Footnotes
[1] Jessica Saunders et al., Rand Center on Quality Policing, Enforcing Immigration Law At The State and Local Levels 1 (2010), https://www.rand.org/content/dam/rand/pubs/occasional_papers/2010/RAND_OP273.pdf.
[2] Francis Wilkinson, Why Trump Deports Fewer Immigrants than Obama: Sanctuary States and Cities Are Slowing the Expulsions, BLOOMBERG (May 15, 2018), https://www.bloomberg.com/view/articles/2018-05-15/trump-is-deporting-fewer-immigrants-than-obama-did.
[3] Id.
[4] Nicole Narea, Trump is deporting way fewer people than Obama did. Why? Vox (Jun. 17, 2025) https://www.vox.com/politics/416901/trump-mass-deportation-obama-border-raids-ice
[5] Tim Henderson, Voluntary Departures Spike As Immigrants Face Squalid Detention, Pressure To Leave, Stateline, May 26, 2025 https://stateline.org/2026/05/26/voluntary-departures-spike-as-immigrants-face-squalid-detention-pressure-to-leave/
[6] https://www.justice.gov/ag/us-sanctuary-jurisdiction-list-following-executive-order-14287-protecting-american-communities; Executive Order 14287 of April 28, 2025 2025-07789 (90 FR 18761) Protecting American Communities from Criminal Aliens, https://www.federalregister.gov/documents/2025/05/02/2025-07789/protecting-american-communities-from-criminal-aliens
[7] Undocumented immigrants are arrested for crimes at between half and a quarter of the rate of native-born U.S. Citizens. National Institute of Justice, U.S. Dep’t of Justice, Undocumented Immigrant Offending Rate Lower Than U.S.-Born Citizen Rate (2024).
[8] Brian Bennett, What the Data Reveals About Trump’s Push to Arrest and Deport More Migrants, Time, Jun. 11, 2025, https://time.com/7292939/trump-deportations-ice-arrests/; Narea, supra note 4.
[9] https://www.reuters.com/world/ice-struggles-vet-recruits-amid-us-immigration-enforcement-push-internal-email-2026-02-26/
[10] Christopher Lasch, Immigration Pol’y Ctr., The Faulty Legal Arguments Behind Immigration Detainers 7 (2013), https://www.americanimmigrationcouncil.org/sites/default/files/research/lasch_on_detainers.pdf; Vermont Criminal Justice Training Council, Fair and Impartial Policing Policy(2017), https://vcjtc.vermont.gov/content/model-fair-and-impartial-policing-policy
[11] https://www.justice.gov/opa/pr/justice-department-publishes-list-sanctuary-jurisdictions; https://www.justice.gov/ag/us-sanctuary-jurisdiction-list-following-executive-order-14287-protecting-american-communities; https://www.nbcconnecticut.com/news/local/ice-arrests-65-undocumented-immigrants-in-four-day-sweep-in-connecticut/3627816/. Despite its 2020 State Supreme Court ruling that preventing state and local law enforcement from conducting immigration arrests, Montana was not included on the Trump Administration’s list. https://www.justice.gov/ag/us-sanctuary-jurisdiction-list-following-executive-order-14287-protecting-american-communities
[12] 567 U.S. 387, 408 (2012)
[13] Ben Levey, Disrupting the Jail-to-Deportation Pipeline in Wisconsin, 2023 Wis. L. Rev. 2027, 2037 (2023); 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/
[14] Marina Johnson, Louisville Removed From DOJ ‘Sanctuary Jurisdictions’ List After Recent Policy Changes, Louisville Courier Journal (Aug. 6, 2025) https://www.courier-journal.com/story/news/politics/2025/08/06/doj-removes-louisville-from-sanctuary-jurisdictions-list/85538326007/; Auditi Guha, Vermont wrongly labeled by feds as a sanctuary jurisdiction, Gov. Scott says (Aug. 19, 2025) https://vtdigger.org/2025/08/19/vermont-wrongly-labeled-by-feds-as-a-sanctuary-jurisdiction-gov-scott-says/
[16] Galarza v. Szalczyk, 745 F.3d 634, 645 (3d Cir. 2014).
[17] U.S. v. Colorado, No. 25-cv-01391-GPG-KAS (D.C. Col. 2026); U.S. v. Illinois, No. 25 CV 1285 (D.C. Ill. 2026).