concurring.
While I join the opinion of the Court, which sufficiently establishes that none of our Fourth Amendment decisions supports the search conducted in this case, I add this concurring opinion to elaborate on my views as to the meaning of the Fourth Amendment in this context. We are confronted here with the all-too-familiar necessity of reconciling a legitimate need of government with constitutionally protected rights. There can be no question as to the seriousness and legitimacy of the law enforcement problem with respect to enforcing along thousands of miles of open border valid immigration and related laws. Nor can there be any question as to the necessity, in our free society, of safeguarding persons against searches and seizures proscribed by the Fourth Amendment. I believe that a resolution of the issue raised by this case is possible with due recognition of both of these interests, and in a manner compatible with the prior decisions of this Court.1
I
The search here involved was carried out as part of a roving search of automobiles in an area generally proximate to the Mexican border. It was not a border search, *276nor can it fairly be said to have been a search conducted at the “functional equivalent” of the border. Nor does this case involve the constitutional propriety of searches at permanent or temporary checkpoints removed from the border or its functional equivalent. Nor, finally, was the search based on cause in the ordinary sense of specific knowledge concerning an automobile or its passengers.2 The question posed, rather, is whether and under what circumstances the Border Patrol may lawfully conduct roving searches of automobiles in areas not far removed from the border for the purpose of apprehending aliens illegally entering or in the country.
The Government has made a convincing showing that large numbers of aliens cross our borders illegally at places other than established crossing points, that they are often assisted by smugglers, that even those who cross on foot are met and transported to their destinations by automobiles, and that roving checks of automobiles are the only feasible means of apprehending them. It would, of course, be wholly impracticable to maintain a constant, patrol along thousands of miles of border. Moreover, because many of these aliens cross the border on foot, or at places other than established checkpoints, it is simply not possible in most cases for the Government to obtain specific knowledge that a person riding or stowed in an automobile is an alien illegally in the coun*277try. Thus the magnitude of the problem is clear. An answer, reconciling the obvious needs of law enforcement with relevant constitutional rights, is far less clear.
II
The Government’s argument to sustain the search here is simply that it was reasonable under the circumstances. But it is by now axiomatic that the Fourth Amendment’s proscription of “unreasonable searches and seizures” is to be read in conjunction with its command that “no Warrants shall issue, but upon probable cause.” Under our cases, both the concept of probable cause and the requirement of a warrant bear on the reasonableness of a search, though. in certain limited circumstances neither is required.
Before deciding whether a warrant is required, I will first address the threshold question of whether some functional equivalent of probable cause may exist for the type of search conducted in this case. The problem of ascertaining the meaning of the probable-cause requirement in the context of roving searches of the sort conducted here is measurably assisted by the Court’s opinion in Camara v. Municipal Court, 387 U. S. 523 (1967), on which the Government relies heavily. The Court was there concerned with the nature of the probable-cause requirement in the context of searches to identify housing code violations and was persuaded that the only workable method of enforcement was periodic inspection of all structures:
“It is here that the probable cause debate is focused, for the agency’s decision to conduct an area inspection is unavoidably based on its appraisal of conditions in the area as a whole, not on its knowledge of conditions in each particular building.” Id., at 536.
*278In concluding that such general knowledge met the probable-cause requirement under those circumstances, the Court took note of a “long history of judicial and public acceptance,” of the absence of other methods for vindicating the public interest in preventing or abating dangerous conditions, and of the limited invasion of privacy occasioned by administrative inspections which are “neither personal in nature nor aimed at the discovery of evidence of crime.” Id., at 537.
Roving automobile searches in border regions for aliens, likewise, have been consistently approved by the judiciary. While the question is one of first impression in this Court, such searches uniformly have been sustained by the courts of appeals whose jurisdictions include those areas of the border between Mexico and the United States where the problem has been most severe. See, e. g., United States v. Miranda, 426 F. 2d 283 (CA9 1970); Roa-Rodriquez v. United States, 410 F. 2d 1206 (CA10 1969). Moreover, as noted above, no alternative solution is reasonably possible.
The Government further argues that such searches resemble those conducted in Camara in that they are undertaken primarily for administrative rather than prosecutorial purposes, that their function is simply to locate those who are illegally here and to deport them. Brief for the United States 28 n. 25. This argument is supported by the assertion that only 3% of aliens apprehended in this country are prosecuted. While the low rate of prosecution offers no great solace to the innocent whose automobiles are searched or to the few who are prosecuted, it does serve to differentiate this class of searches from random area searches which are no more than “fishing expeditions” for evidence to support prosecutions. The possibility of prosecution does not distinguish such searches from those involved in Camara. Despite the Court’s assertion in that case that the searches *279were not “aimed at the discovery of evidence of crime,” 387 U. S., at 537, violators of the housing code there were subject to criminal penalties. Id., at 527 n. 2.
Of perhaps greater weight is the fact that these searches, according to the Government, are conducted in areas where the concentration of illegally present aliens is high, both in absolute terms and in proportion to the number of persons legally present. While these searches are not border searches in the conventional sense, they are incidental to the protection of the border and draw a large measure of justification from the Government’s extraordinary responsibilities and powers with respect to the border. Finally, and significantly, these are searches of automobiles rather than searches of persons or buildings. The search of an automobile is far less intrusive on the rights protected by the Fourth Amendment than the search of one’s person or of a building. This Court “has long distinguished between an automobile and a home or office.” Chambers v. Maroney, 399 U. S. 42, 48 (1970). As the Government has demonstrated, and as those in the affected areas surely know, it is the automobile which in most cases makes effective the attempts to smuggle aliens into this country.
The conjunction of these factors — consistent judicial approval, absence of a reasonable alternative for the solution of a serious problem, and only a modest intrusion on those whose automobiles are searched — persuades me that under appropriate limiting circumstances there may exist a constitutionally adequate equivalent of probable cause to conduct roving vehicular searches in border areas.
Ill
The conclusion that there may be probable cause to conduct roving searches does not end the inquiry, for “except in certain carefully defined classes of cases, a search of private property without proper consent is *280'unreasonable’ unless it has been authorized by a valid search warrant.” Camara v. Municipal Court, supra, at 528-529. I expressed the view last Term that the warrant clause reflects an important policy determination: “The Fourth Amendment does not contemplate the executive officers of Government as neutral and disinterested magistrates. Their duty and responsibility is to enforce the laws, to investigate, and to prosecute. . . . But those charged with this investigative and prosecutorial duty should not be the sole judges of when to utilize constitutionally sensitive means in pursuing their tasks.” United States v. United States District Court, 407 U. S. 297, 317 (1972). See also Coolidge v. New Hampshire, 403 U. S. 443, 481 (1971); Chimel v. California, 395 U. S. 752, 763-764 (1969).
To justify warrantless searches in circumstances like those presented in this case, the Government relies upon several of this Court’s decisions recognizing exceptions to the warrant requirement. A brief review of the nature of each of these major exceptions illuminates the relevant considerations in the present case. In Terry v. Ohio, 392 U. S. 1 (1968), the Court held that a policeman may conduct a limited “pat down” search for weapons when he has reasonable grounds for believing that criminal conduct has taken or is taking place and that the person he searches is armed and dangerous. “The sole justification [for such a] search ... is the protection of the police officer and others nearby . . . .” Id., at 29. Nothing in Terry supports an exception to the warrant requirement here.
Colonnade Catering Corp. v. United States, 397 U. S. 72 (1970), and United States v. Biswell, 406 U. S. 311 (1972), on which the Government also relies, both concerned the standards which govern inspections of the business premises of those with federal licenses to engage in the sale of liquor, Colonnade, or the sale of guns, *281Biswell. In those cases, Congress was held to have power to authorize warrantless searches. As the Court stated in Biswell:
“When a dealer chooses to engage in this pervasively regulated business and to accept a federal license, he does so with the knowledge that his business records, firearms, and ammunition will be subject to effective inspection.” 406 U. S., at 316.
Colonnade and Biswell cannot fairly be read to cover cases of the present type. One who merely travels in regions near the borders of the country can hardly be thought to have submitted to inspections in exchange for a special perquisite.
More closely in point on their facts are the cases involving automobile searches. E. g., Carroll v. United States, 267 U. S. 132 (1925); Chambers v. Maroney, supra; Coolidge v. New Hampshire, supra. But while those cases allow automobiles to be searched without a warrant in certain circumstances, the principal rationale for this exception to the warrant clause is that under those circumstances “it is not practicable to secure a warrant because the vehicle can be quickly moved out of the locality or jurisdiction in which the warrant must be sought.” Carroll v. United States, supra, at 153. The .Court today correctly poiiits out that a warrant-less search under the Carroll line of cases must be supported by probable cause in the sense of specific knowledge about a particular automobile. While, as indicated above, my view is that on appropriate facts the Government can satisfy the probable cause requirement for a roving search in a border area without possessing information about particular automobiles, it does not follow that the warrant requirement is inapposite. The very fact that the Government’s supporting information relates to criminal activity in certain areas rather than *282to evidence about a particular automobile renders irrelevant the justification for warrantless searches relied upon in Carroll and its progeny. Quite simply, the roving searches are justified by experience with obviously non-mobile sections of a particular road or area embracing several roads.
None of the foregoing exceptions to the warrant requirement, then, applies to roving automobile searches in border areas. Moreover, the propriety of the warrant procedure here is affirmatively established by Camara. See also See v. City of Seattle, 387 U. S. 541 (1967). For the reasons outlined above, the Court there ruled that probable cause could be shown for an area search, but nonetheless required that a warrant be obtained for unconsented searches. The Court indicated its general approach to exceptions to the warrant requirement:
“In assessing whether the public interest demands creation of a general exception to the Fourth Amendment's warrant requirement, the question is not whether the public interest justifies the type of search in question, but whether the authority to search should be evidenced by a warrant, which in turn depends in part upon whether the burden of obtaining a warrant is likely to frustrate the governmental purpose behind the search.” Camara v. Municipal Court, supra, at 533.
See also United States v. United States District Court, supra, at 315.
The Government argues that Camara and See are distinguishable from the present case for the purposes of the warrant requirement. It is true that while a building inspector who is refused admission to a building may easily obtain a warrant to search that building, a member of the Border Patrol has no such opportunity when *283he is refused permission to inspect an automobile. It is also true that the judicial function envisioned in Camara did not extend to reconsideration of “the basic agency decision to canvass an area,” Camara v. Municipal Court, supra, at 532, while the judicial function here would necessarily include passing on just such a basic decision.
But it does not follow from these distinctions that “no warrant system can be constructed that would be feasible and meaningful.” Brief for the United States 36. Nothing in the papers before us demonstrates that it would not be feasible for the Border Patrol to obtain advance judicial approval of the decision to conduct roving searches on a particular road or roads for a reasonable period of time.3 According to the Government, the incidence of illegal transportation of aliens on certain roads is predictable, and the roving searches are apparently planned in advance or carried out according to a predetermined schedule. The use of an area warrant procedure would surely not “frustrate the governmental purpose behind the search.” Camara v. Municipal Court, supra, at 533. It would of course entail some inconvenience, but inconvenience alone has never been thought to be an adequate reason for abrogating the warrant requirement. E. g., United States v. United States District Court, supra, at 321.
Although standards for probable cause in the context of this case are relatively unstructured (cf. id., at 322), there are a number of relevant factors which would merit consideration: they include (i) the frequency with which aliens illegally in the country are known or reasonably believed to be transported within a particular area; *284(ii) the proximity of the area in question to the border; (iii) the extensiveness and geographic characteristics of the area, including the roads therein and the extent of their use,4 and (iv) the probable degree of interference with the rights of innocent persons, taking into account the scope of the proposed search, its duration, and the concentration of illegal alien traffic in relation to the general traffic of the road or area.
In short, the determination of whether a warrant should be issued for an area search involves a balancing of the legitimate interests of law enforcement with protected Fourth Amendment rights. This presents the type of delicate question of constitutional judgment which ought to be resolved by the Judiciary rather than the Executive. In the words of Camara,
“This is precisely the discretion to invade private property which we have consistently circumscribed by a requirement that a disinterested party warrant the need to search.” 387 U. S., at 532-533.
Nor does the novelty of the problem posed by roving searches in border areas undermine the importance of a prior judicial determination. When faced with a similarly unconventional problem last Term in United States District Court, supra, we recognized that the focus of the search there involved was “less precise than that directed against more conventional types of crime,” and that “[different standards may be compatible with the Fourth Amendment if they are reasonable both in rela*285tion to the legitimate need of Government . . . and the protected rights of our citizens.” 407 U. S., at 322-323. Yet we refused to abandon the Fourth Amendment commitment to the use of search warrants whenever this is feasible with due regard to the interests affected.
For the reasons stated above, I think a rational search warrant procedure is feasible in cases of this kind. As no warrant was obtained here, I agree that the judgment must be reversed. I express no opinion as to whether there was probable cause to issue a warrant on the facts of this particular case.
I am in accord with the Court’s conclusion that nothing in § 287 (a) (3) of the Immigration and Nationality Act, 8 U. S. C. § 1357 (a) (3), or in 8 CFR § 287.1 serves to authorize an otherwise unconstitutional search.
The Solicitor General’s brief in this Court states explicitly that “We ... do not take the position that the checking operations are justified, because the officers have probable cause or even ‘reasonable suspicion’ to believe, with respect to each vehicle checked, that it contains an illegal alien. Apart from the reasonableness of establishment of the checking operation in this case, there is nothing in the record to indicate that the Border Patrol officers had any special or particular reason to stop petitioner and examine his car.” Brief for the United States 9-10.
There is no reason why a judicial officer could not approve where appropriate a series of roving searches over the course of several days or weeks. Experience with an initial search or series of searches would be highly relevant in considering applications for renewal of a warrant.
Depending upon the circumstances, there may be probable cause for the search to be authorized only for a designated portion of a particular road or such cause may exist for a designated area which may contain one or more roads or tracks. Particularly along much of the Mexican border, there are vast areas of uninhabited desert and arid land which are traversed by few, if any, main roads or highways, but which nevertheless may afford opportunities — by virtue of their isolated character — for the smuggling of aliens.