The Fourth Amendment to the Constitution prohibits “unreasonable searches and seizures.” It applies to all seizures of a person, including seizures that involve only a brief detention short of traditional arrest. As interpreted by the Supreme Court in an immigration context, except at the border, the Fourth Amendment prohibits immigration enforcement officers to make detentive stops unless they are aware of “specific articulable facts that reasonably warrant suspicion” that the person detained may be illegally in the country. Reasonable suspicion cannot be based on “generalizations” that, if accepted, would cast suspicion on large segments of the law-abiding population. On June 6, 2025, federal law enforcement arrived in Los Angeles to participate in what federal officials have described as “the largest Mass Deportation Operation . . . in History.” U.S. Customs and Border Patrol agents and officers were sent to join officers from the Enforcement and Removal Operations directorate of U.S. Immigration and Customs Enforcement (“ICE”) to carry out “Operation At Large” in Los Angeles, California. This operation involved teams of three to five agents who temporarily detained individuals in public places such as streets, sidewalks, and publicly accessible portions of businesses, and made arrests for immigration violations. On July 2, five individual plaintiffs and three membership associations sued twelve senior federal officials, who share responsibility for directing federal immigration enforcement in the Los Angeles area, alleging a violation of the Fourth Amendment. Perdomo v. Noem (C. D. Cal). The complaint asserts that by an ongoing policy and/or practice, detentive stops in the Central District of California were being conducted without reasonable suspicion that the person to be stopped is within the United States in violation of U.S. immigration law. Reviewing the evidence offered by the plaintiffs in support of an injunction pending further litigation, the district court found that circumstances surrounding the stops were coercive enough that the interactions were not consensual. The district court also found that the plaintiffs are “likely to succeed in showing that seizures were based only upon four enumerated factors” or a subset of them. Those factors were (1) apparent race or ethnicity; (2) speaking Spanish or speaking English with an accent; (3) presence at a particular location; and (4) the type of work one does. The district court then concluded that in the context of the Central District of California, those four enumerated factors — even when considered together — describe only a broad profile and “do not demonstrate reasonable suspicion for any particular stop.” Moreover, the court determined that, despite there being no evidence of an “official policy” of making stops based only on the four factors and without reasonable suspicion, there was sufficient evidence to show that defendants’ agents were routinely doing so. Premised on these conclusions, on July 11, the district enjoined the defendant officials from relying solely on the factors below, alone or in combination, to form reasonable suspicion for a detentive stop: Apparent race or ethnicity; Speaking Spanish or speaking English with an accent; Presence at a particular location (e.g., bus stop, car wash, tow yard, day laborer pick up site, agricultural site, etc.); or The type of work one does. The administration appealed the district court’s order to the Ninth Circuit Court of Appeals which refused to intervene. Perdomo v. Noem (July 28). The three judge panel determined that “a characteristic common to both legal and illegal immigrants does little to arouse reasonable suspicion.” In the U.S. generally, apparent Hispanic or Latino race or ethnicity generally has limited probative value, because large numbers of native-born and naturalized citizens have the physical characteristics identified with Hispanic or Latino ethnicity. Speaking Spanish and speaking English with an accent are likewise characteristics that apply to a sizable portion of individuals lawfully present in this country. As to location, the Supreme Court has made clear that an individual’s presence at a location that illegal immigrants are known to frequent does little to support reasonable suspicion when U.S. citizens and legal immigrants are also likely to be present at those locations. US v. Brignoni (1975). Like location, the type of work one does is at most “marginally relevant” to establishing reasonable suspicion, even if it is work commonly performed by immigrants without legal status. Evidence that a particular employer is employing a large number of undocumented workers does not create reasonable suspicion as to each individual employee. On August 7, the administration once more sought emergency relief from the Supreme Court. In doing so, the Solicitor General asserts that the injunction entered puts “a straitjacket on law-enforcement efforts.” Although this case arises out of ICE activities in Southern California, the Supreme Court’s ultimate decision will have obvious implications for the practices of ICE agents nationwide. John Christie was for many years a senior partner in a large Washington, D.C. law firm. He specialized in anti-trust litigation and developed a keen interest in the U.S. Supreme Court about which he lectures and writes.