opinion: IMMIGRATION AND NATURALIZATION SERVICE et al. v. DELGADO et al.
  No. 82-1271.
  Argued January 11, 1984
  Decided April 17, 1984
  Rehnquist, J., delivered the opinion of the Court, in which Burger, C. J., and White, Blackmun, Stevens, and O’Connor, JJ., joined. Stevens, J., filed a concurring opinion, post, p. 221. Powell, J., filed an opinion concurring in the result, post, p. 221. Brennan, J., filed an opinion concurring in part and dissenting in part, in which Marshall, J., joined, post, p. 225.
  Deputy Solicitor General Frey argued the cause for petitioners. With him on the briefs were Solicitor General Lee, Assistant Attorney General Trott, Elliott Schulder, and Patty Merkamp Stemler.
  Henry R. Fenton argued the cause for respondents. With him on the brief were Gordon K. Hubei and Max Zimny
  Briefs of amici curiae urging affirmance were filed for the American Civil Liberties Union by David M. Brodsky, Burt Neubome, and Charles S. Sims; and for the Mexican American Legal Defense and Education Fund, Inc., et al. by Michael Kantor and Alan Diamond.
  Justice Rehnquist
  delivered the opinion of the Court.
  In the course of enforcing the immigration laws, petitioner Immigration and Naturalization Service (INS) enters employers’ worksites to determine whether any illegal aliens may be present as employees. The Court of Appeals for the Ninth Circuit held that the “factory surveys” involved in this case amounted to a seizure of the entire work forces, and further held that the INS could not question individual employees during any of these surveys unless its agents had a reasonable suspicion that the employee to be questioned was an illegal alien. International Ladies’ Garment Workers’ Union, AFL-CIO v. Sureck, 681 F. 2d 624 (1982). We conclude that these factory surveys did not result in the seizure of the entire work forces, and that the individual questioning of the respondents in this case by INS agents concerning their citizenship did not amount to a detention or seizure under the Fourth Amendment. Accordingly, we reverse the judgment of the Court of Appeals.
  Acting pursuant to two warrants, in January and September 1977, the INS conducted a survey of the work force at Southern California Davis Pleating Co. (Davis Pleating) in search of illegal aliens. The warrants were issued on a showing of probable cause by the INS that numerous illegal aliens were employed at Davis Pleating, although neither of the search warrants identified any particular illegal aliens by name. A third factory survey was conducted with the employer’s consent in October 1977, at Mr. Pleat, another garment factory.
  At the beginning of the surveys several agents positioned themselves near the buildings’ exits, while other agents dispersed throughout the factory to question most, but not all, employees at their work stations. The agents displayed badges, carried walkie-talkies, and were armed, although at no point during any of the surveys was a weapon ever drawn. Moving systematically through the factory, the agents approached employees and, after identifying themselves, asked them from one to three questions relating to their citizenship. If the employee gave a credible reply that he was a United States citizen, the questioning ended, and the agent moved on to another employee. If the employee gave an unsatisfactory response or admitted that he was an alien, the employee was asked to produce his immigration papers. During the survey, employees continued with their work and were free to walk around within the factory.
  Respondents are four employees questioned in one of the three surveys. In 1978 respondents and their union representative, the International Ladies Garment Workers’ Union, filed two actions, later consolidated, in the United States District Court for the Central District of California challenging the constitutionality of INS factory surveys and seeking declaratory and injunctive relief. Respondents argued that the factory surveys violated their Fourth Amendment right to be free from unreasonable searches or seizures and the equal protection component of the Due Process Clause of the Fifth Amendment.
  The District Court denied class certification and dismissed the union from the action for lack of standing, App. to Pet. for Cert. 58a-60a. In a series of cross-motions for partial summary judgment, the District Court ruled that respondents had no reasonable expectation of privacy in their workplaces which conferred standing on them to challenge entry by the INS pursuant to a warrant or owner’s consent. Id., at 49a-52a, 53a-55a, 56a-57a. In its final ruling the District Court addressed respondents’ request for injunctive relief directed at preventing the INS from questioning them personally during any future surveys. The District Court, with no material facts in dispute, found that each of the four respondents was asked a question or questions by an INS agent during one of the factory surveys. Id., at 46a. Reasoning from this Court’s decision in Terry v. Ohio, 392 U. S. 1 (1968), that law enforcement officers may ask questions of anyone, the District Court ruled that none of the respondents had been detained under the Fourth Amendment during the factory surveys, either when they were questioned or otherwise. App. to Pet. for Cert. 47a. Accordingly, it granted summary judgment in favor of the INS.
  The Court of Appeals reversed. Applying the standard first enunciated by a Member of this Court in United States v. Mendenhall, 446 U. S. 544 (1980) (opinion of Stewart, J.), the Court of Appeals concluded that the entire work forces were seized for the duration of each survey, which lasted from one to two hours, because the stationing of agents at the doors to the buildings meant that “a reasonable worker ‘would have believed that he was not free to leave.’” 681 F. 2d, at 634 (quoting United States v. Anderson, 663 F. 2d 934, 939 (CA9 1981)). Although the Court of Appeals conceded that the INS had statutory authority to question any alien or person believed to be an alien as to his right to be or remain in the United States, see 66 Stat. 233, 8 U. S. C. § 1357(a)(1), it further held that under the Fourth Amendment individual employees could be questioned only on the basis of a reasonable suspicion that a particular employee being questioned was an alien illegally in the country. 681 F. 2d, at 639-645. A reasonable suspicion or probable cause to believe that a number of illegal aliens were working at a particular factory site was insufficient to justify questioning any individual employee. Id., at 643. Consequently, it also held that the individual questioning of respondents violated the Fourth Amendment because there had been no such reasonable suspicion or probable cause as to any of them.
  We granted certiorari to review the decision of the Court of Appeals, 461 U. S. 904 (1983), because it has serious implications for the enforcement of the immigration laws and presents a conflict with the decision reached by the Third Circuit in Babula v. INS, 665 F. 2d 293 (1981).
  The Fourth Amendment does not proscribe all contact between the police and citizens, but is designed “to prevent arbitrary and oppressive interference by enforcement officials with the privacy and personal security of individuals.” United States v. Martinez-Fuerte, 428 U. S. 543, 554 (1976). Given the diversity of encounters between police officers and citizens, however, the Court has been cautious in defining the limits imposed by the Fourth Amendment on encounters between the police and citizens. As we have noted elsewhere: “Obviously, not all personal intercourse between policemen and citizens involves ‘seizures’ of persons. Only when the officer, by means of physical force or show of authority, has restrained the liberty of a citizen may we conclude that a ‘seizure’ has occurred.” Terry v. Ohio, supra, at 19, n. 16. While applying such a test is relatively straightforward in a situation resembling a traditional arrest, see Dunaway v. New York, 442 U. S. 200, 212-216 (1979), the protection against unreasonable seizures also extends to “seizures that involve only a brief detention short of traditional arrest.” United States v. Brignoni-Ponce, 422 U. S. 873, 878 (1975). What has evolved from our cases is a determination that an initially consensual encounter between a police officer and a citizen can be transformed into a seizure or detention within the meaning of the Fourth Amendment, “if, in view of all the circumstances surrounding the incident, a reasonable person would have believed that he was not free to leave.” Mendenhall, supra, at 554 (footnote omitted); see Florida v. Royer, 460 U. S. 491, 502 (1983) (plurality opinion).
  Although we have yet to rule directly on whether mere questioning of an individual by a police official, without more, can amount to a seizure under the Fourth Amendment, our recent decision in Royer, supra, plainly implies that interrogation relating to one’s identity or a request for identification by the police does not, by itself, constitute a Fourth Amendment seizure. In Royer, when Drug Enforcement Administration agents found that the respondent matched a drug courier profile, the agents approached the defendant and asked him for his airplane ticket and driver’s license, which the agents then examined. A majority of the Court believed that the request and examination of the documents were "permissible in themselves.” Id., at 501 (plurality opinion); see id., at 523, n. 3 (opinion of Rehnquist, J.). In contrast, a much different situation prevailed in Brown v. Texas, 443 U. S. 47 (1979), when two policemen physically detained the defendant to determine his identity, after the defendant refused the officers’ request to identify himself. The Court held that absent some reasonable suspicion of misconduct, the detention of the defendant to determine his identity violated the defendant’s Fourth Amendment right to be free from an unreasonable seizure. Id., at 52.
  What is apparent from Royer and Brown is that police questioning, by itself, is unlikely to result in a Fourth Amendment violation. While most citizens will respond to a police request, the fact that people do so, and do so without being told they are free not to respond, hardly eliminates the consensual nature of the response. Cf. Schneckloth v. Bustamonte, 412 U. S. 218, 231-234 (1973). Unless the circumstances of the encounter are so intimidating as to demonstrate that a reasonable person would have believed he was not free to leave if he had not responded, one cannot say that the questioning resulted in a detention under the Fourth Amendment. But if the person refuses to answer and the police take additional steps — such as those taken in Brown— to obtain an answer, then the Fourth Amendment imposes some minimal level of objective justification to validate the detention or seizure. United States v. Mendenhall, 446 U. S., at 554; see Terry v. Ohio, 392 U. S., at 21.
  The Court of Appeals held that “the manner in which the factory surveys were conducted in this case constituted a seizure of the workforce” under the Fourth Amendment. 681 F. 2d, at 634. While the element of surprise and the systematic questioning of individual workers by several INS agents contributed to the court’s holding, the pivotal factor in its decision was the stationing of INS agents near the exits of the factory buildings. According to the Court of Appeals, the stationing of agents near the doors meant that “departures were not to be contemplated,” and thus, workers were “not free to leave.” Ibid. In support of the decision below, respondents argue that the INS created an intimidating psychological environment when it intruded unexpectedly into the workplace with such a show of officers. Besides the stationing of agents near the exits, respondents add that the length of the survey and the failure to inform workers they were free to leave resulted in a Fourth Amendment seizure of the entire work force.
  We reject the claim that the entire work forces of the two factories were seized for the duration of the surveys when the INS placed agents near the exits of the factory sites. Ordinarily, when people are at work their freedom to move about has been meaningfully restricted, not by the actions of law enforcement officials, but by the workers’ voluntary obligations to their employers. The record indicates that when these surveys were initiated, the employees were about their ordinary business, operating machinery and performing other job assignments. While the surveys did cause some disruption, including the efforts of some workers to hide, the record also indicates that workers were not prevented by the agents from moving about the factories.
  Respondents argue, however, that the stationing of agents near the factory doors showed the INS’s intent to prevent people from leaving. But there is nothing in the record indicating that this is what the agents at the doors actually did. The obvious purpose of the agents’ presence at the factory doors was to insure that all persons in the factories were questioned. The record indicates that the INS agents’ conduct in this case consisted simply of questioning employees and arresting those they had probable cause to believe were unlawfully present in the factory. This conduct should have given respondents no reason to believe that they would be detained if they gave truthful answers to the questions put to them or if they simply refused to answer. If mere questioning does not constitute a seizure when it occurs inside the factory, it is no more a seizure when it occurs at the exits.
  A similar conclusion holds true for all other citizens or aliens lawfully present inside the factory buildings during the surveys. The presence of agents by the exits posed no reasonable threat of detention to these workers while they walked throughout the factories on job assignments. Likewise, the mere possibility that they would be questioned if they sought to leave the buildings should not have resulted in any reasonable apprehension by any of them that they would be seized or detained in any meaningful way. Since most workers could have had no reasonable fear that they would be detained upon leaving, we conclude that the work forces as a whole were not seized.
  The Court of Appeals also held that “detentive questioning” of individuals could be conducted only if INS agents could articulate “objective facts providing investigators with a reasonable suspicion that each questioned person, so detained, is an alien illegally in this country.” 681 F. 2d, at 638. Under our analysis, however, since there was no seizure of the work forces by virtue of the method of conducting the factory surveys, the only way the issue of individual questioning could be presented would be if one of the named respondents had in fact been seized or detained. Reviewing the deposition testimony of respondents, we conclude that none were.
  The questioning of each respondent by INS agents seems to have been nothing more than a brief encounter. None of the three Davis Pleating employees were questioned during the January survey. During the September survey at Davis Pleating, respondent Delgado was discussing the survey with another employee when two INS agents approached him and asked him where he was from and from what city. When Delgado informed them that he came from Mayaguez, Puerto Rico, the agent made an innocuous observation to his partner and left. App. 94. Respondent Correa's experience in the September survey was similar. Walking from one part of the factory to another, Correa was stopped by an INS agent and asked where she was bom. When she replied “Huntington Park, [California],” the agent walked away and Correa continued about her business. Id., at 115. Respondent Labonte, the third Davis Pleating employee, was tapped on the shoulder and asked in Spanish, “Where are your papers?” Id., at 138. Labonte responded that she had her papers and without any further request from the INS agents, showed the papers to the agents, who then left. Finally, respondent Miramontes, the sole Mr. Pleat employee involved in this case, encountered an agent en route from an office to her worksite. Questioned concerning her citizenship, Miramon-tes replied that she was a resident alien, and on the agent’s request, produced her work permit. The agent then left. Id., at 120-121.
  Respondents argue that the manner in which the surveys were conducted and the attendant disruption caused by the surveys created a psychological environment which made them reasonably afraid they were not free to leave. Consequently, when respondents were approached by INS agents and questioned concerning their citizenship and right to work, they were effectively detained under the Fourth Amendment, since they reasonably feared that refusing to answer would have resulted in their arrest. But it was obvious from the beginning of the surveys that the INS agents were only questioning people. Persons such as respondents who simply went about their business in the workplace were not detained in any way; nothing more occurred than that a question was put to them. While persons who attempted to flee or evade the agents may eventually have been detained for questioning, see id., at 50, 81-84, 91-93, respondents did not do so and were not in fact detained. The manner in which respondents were questioned, given its obvious purpose, could hardly result in a reasonable fear that respondents were not free to continue working or to move about the factory. Respondents may only litigate what happened to them, and our review of their description of the encounters with the INS agents satisfies us that the encounters were classic consensual encounters rather than Fourth Amendment seizures. See Florida v. Royer, 460 U. S. 491 (1983); United States v. Mendenhall, 446 U. S. 544 (1980).
  Accordingly, the judgment of the Court of Appeals is
  Reversed.
  Respondents Herman Delgado, Ramona Correa, and Francisca La-bonte worked at Davis Pleating, while Marie Miramontes, the fourth respondent, was employed by Mr. Pleat. Both Delgado and Correa are United States citizens, while Labonte and Miramontes are permanent resident aliens.
  The District Court never ruled directly on respondents’ Fifth Amendment claim, apparently reasoning that since respondents’ Fourth Amendment rights had not been violated, their Fifth Amendment right had also not been violated. The Court of Appeals also never ruled on respondents’ Fifth Amendment claim, and we decline to do so.
  The Court of Appeals ruled that the District Court did not abuse its discretion in denying class certification. In light of its disposition of respondents’ Fourth Amendment claims, the Court of Appeals declined to resolve the union’s appeal from the District Court’s determination that the union lacked standing to raise its members’ Fourth Amendment claims. 681 F. 2d. at 645. n. 24.
  Although the issue was the subject of substantial discussion at oral argument, the INS does not contest that respondents have standing to bring this case. They allege the existence of an ongoing policy which violated the Fourth Amendment and which will be applied to their workplace in the future. Cf. Allee v. Medrano, 416 U. S. 802 (1974). Part of their argument is clearly based on the INS’s detention of illegal aliens found working at the two factories. Respondents, however, can only premise their right to injunctive relief on their individual encounters with INS agents during the factory surveys. See infra, at 221.
  Contrary to respondents’ assertion, it also makes no difference in this case that the encounters took place inside a factory, a location usually not accessible to the public. The INS officers were lawfully present pursuant to consent or a warrant, and other people were in the area during the INS agents’ questioning. Thus, the same considerations attending contacts between the police and citizens in public places should apply to the questions presented to the individual respondents here.
  In her deposition respondent Miramontes described an incident that occurred during the October factory survey at Mr. Pleat, in which an INS agent stationed by an exit attempted to prevent a worker, presumably an illegal alien, from leaving the premises after the survey started. The worker walked out the door and when an agent tried to stop him, the worker pushed the agent aside and ran away. App. 125-126. An ambiguous, isolated incident such as this fails to provide any basis on which to conclude that respondents have shown an INS policy entitling them to in-junctive relief. See Rizzo v. Goode, 423 U. S. 362 (1976); cf. Allee v. Medrano, supra; Hague v. CIO, 307 U. S. 496 (1939).
  Respondents Delgado and Labonte both left the building during the INS survey, Delgado to load a truck and Labonte to observe INS activities outside the building. App. 98, 136. Neither of them stated in their depositions that the INS agents in any way restrained them from leaving the building, or even addressed any questions to them upon leaving.
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