What are the legal standards for reasonable suspicion and probable cause in immigration stops, and how have courts applied them to questions of race and language?
Executive summary
The constitutional floor for immigration stops remains the Fourth Amendment’s protection against unreasonable searches and seizures: officers need reasonable suspicion to briefly stop and question someone about immigration status, and probable cause to arrest — a higher standard — but the Supreme Court’s recent shadow-docket intervention has loosened lower-court limits on what can count toward that suspicion [1] [2]. The result is an active split between lower courts and advocates who see constitutional guardrails as intact and the Supreme Court’s order and concurrence signaling broader deference to officers’ “totality of the circumstances” judgments that may include race and language as relevant factors [2] [3].
1. Legal standards: reasonable suspicion is less than probable cause but must be articulable
Under long-standing Supreme Court precedent, a brief investigative stop requires reasonable suspicion grounded in specific, articulable facts — a standard lower than probable cause but not mere hunch — while arrests require probable cause that a crime (or in immigration, unlawful presence) has occurred [1] [4]. Lower courts in Perdomo v. Noem applied that framework to bar stops based solely on broad factors like perceived race, speaking Spanish, workplace or location, concluding those factors alone are “insufficient and impermissible” to furnish reasonable suspicion because they are “no more indicative of illegal presence... than of legal presence” [4] [5].
2. How courts have treated race and language historically in immigration stops
Historically the Court has allowed certain contextual factors in immigration policing (Brignoni‑Ponce and later cases), creating a jurisprudence that instructs courts to look at the totality of the circumstances rather than any single trait [3] [1]. Lower courts confronting modern ICE sweeps have pushed back, finding practices that target people for appearing Latino or speaking Spanish likely violate the Fourth Amendment because those traits are not reliable proxies for unlawful presence [4] [5].
3. The Supreme Court’s recent intervention and its practical message
In September 2025 the Supreme Court issued a stay that effectively lifted a district-court injunction limiting ICE stops in Los Angeles, doing so without a full published opinion and thereby leaving the lower court’s reasoning in force only temporarily while signaling tolerance for broader enforcement tactics [2] [6]. A concurrence by Justice Kavanaugh explicitly stated that “apparent ethnicity alone cannot furnish reasonable suspicion” but argued that ethnicity, language, location, and type of work, viewed together under the “totality of the circumstances,” can constitute reasonable suspicion — an approach critics say revives and endorses racialized profiling [2] [7].
4. Competing interpretations and the stakes for civil rights
Civil‑rights and immigrant‑advocacy groups characterize the Court’s order as a green light for racial profiling and warn it will generate unlawful stops, detentions, and fear across communities that speak Spanish or work in industries with many immigrants [8] [6] [5]. Legal scholars and proponents of the stay counter that the Court’s move returns courts to established precedents that permit reliance on officer experience and multiple factors — a pragmatic rule they argue is necessary for effective immigration enforcement [3] [2]. The tension reveals implicit agendas: advocacy groups stress protection of civil liberties and community safety, while government filings emphasize administrative flexibility and operational discretion [6] [2].
5. What lower courts and future litigation are likely to focus on next
Because the Supreme Court’s stay was issued on the emergency docket and carried little written reasoning, lower courts and litigants will litigate whether combinations of factors actually yield constitutionally sufficient reasonable suspicion in specific stops, and whether reliance on race or language crosses the line to unlawful profiling — a factual, record‑heavy inquiry that plaintiffs say the district court already weighed in Perdomo [4] [1]. Observers expect continued suits and appeals aiming to force a full merits decision; until then, the legal landscape remains unsettled and enforcement practice will vary by district and agency posture [6] [9].