REAVLEY, Circuit Judge:
The purpose of this en banc rehearing is to reconsider Fifth Circuit precedent deeming a checkpoint on an interstate highway at Sierra Blanca to be a “functional equivalent of the border.” Appellants' drug law violations were discovered by full searches of their automobiles at this checkpoint. In one case capsules of a controlled substance were found in a cosmetics case in the car trunk; in the other case cocaine was found in a suitcase in the car trunk. Adhering to our prior decisions, a panel of this court upheld the appellants’ convictions, and approved the searches at Sierra Blanca on the ground that this checkpoint is the “functional equivalent of the border.” The en banc court now decides that the Sierra Blanca checkpoint should not have been regarded as a border equivalent. We further hold that the plenary searches presently conducted at the Sierra Blanca checkpoint are unreasonable under the Fourth Amendment. However, given the significant government interest in controlling illegal immigration, we consider the availability of area warrants that would allow inspections for illegal aliens at checkpoints near the border. Finally, we affirm the appellants’ convictions because the instant searches were conducted in good faith reliance upon our earlier decisions.
I
Functional Equivalence and The Sierra Blanca Checkpoint
The circumstances responsible for bringing the appellants before this court have been recited previously, and need not be repeated here. See United States v. Jackson, 807 F.2d 1185, 1187-90 (5th Cir.1986); United States v. Oyarzun, 760 F.2d 570, 572-73 (5th Cir.1985). Instead, we begin by telling how the Fifth Circuit developed its own functional equivalent for controlling Fourth Amendment law.
The Supreme Court first coined the phrase “functional equivalent” of the border in Almeida-Sanchez v. United States, 413 U.S. 266, 272-73, 93 S.Ct. 2535, 2539, 37 L.Ed.2d 596 (1973), describing two possible examples as follows:
[Searches at an established station near the border, at a point marking the confluence of two or more roads that extend from the border, might be functional equivalents of border searches. For another example, a search of the passengers and cargo of an airplane arriving at a St. Louis airport after a nonstop flight from Mexico City would clearly be the functional equivalent of a border search.
The Almeida-Sanchez Court did not otherwise explain the meaning of this new concept, nor has the Court since elaborated its [855]*855understanding of what types of checkpoints qualify as functionally equivalent to the border. The circuit courts, however, have examined in some detail the notion of functionally equivalent borders. In this section we consider the Fifth Circuit’s use of the term.
The Sierra Blanca checkpoint served as the proving ground for this court’s first interpretation of the phrase “functional equivalent” of the border in United States v. Hart, 506 F.2d 887 (5th Cir.) (Hart I), vacated and remanded, 422 U.S. 1053, 95 S.Ct. 2674, 45 L.Ed.2d 706 (1975), reaffd on remand, 525 F.2d 1199 (5th Cir.) (Hart II), cert. denied, 428 U.S. 923, 96 S.Ct. 3234, 49 L.Ed.2d 1226 (1976).1 The defendant in Hart I was arrested after a border patrol agent discovered approximately 397 pounds of marijuana in the trunk of his car following a routine search at the checkpoint. The Hart I court interpreted the Supreme Court’s functional equivalency concept broadly, believing that it referred to the same permanent checkpoints for which we had long upheld warrantless searches for illegal aliens. 506 F.2d at 889-92 n. 1 (see cites contained therein).2 The court identified three characteristics that “transform” a checkpoint into the border’s functional equivalent and make searches there reasonable: “the proximity of the checkpoint to the border, the permanent nature of the checkpoint and the hours of operation.” Id. at 895. The original rationale for affixing the “functional equivalent” label to the Sierra Blanca checkpoint, therefore, did not depend on its functioning the same as actual border checkpoints where traffic is stopped as it enters the country; it was based on the reasonableness, under the Fourth Amendment, of stopping vehicles in the border region to check passengers’ citizenship status under 8 U.S.C. § 1357(a)(3).3 Id. at 894. The court explained as follows:
[AJlong much of the Mexican-United States border runs the Rio Grande River, [856]*856which, in spite of a name indicating contrary magnificence, can be driven across, waded across, and easily swim across at all times, and much of the time can be walked across without wetting a foot. With so much access to a highway parallel to the border by aliens who could easily have walked across the border, we think the Fourth Amendment rule of reason would permit a search for those aliens of vehicles that may have taken them aboard after their arrival by other means within our boundaries. With almost 2000 miles of Mexican border from Brownsville, Texas to San Diego, California, contiguous to four of the states of the Union, the impracticality of guarding every part where human crossing could be made should be so apparent as to make inexorably reasonable some method of curtailing illegal entry such as established at the Sierra Blanca checkpoint.
Id. at 897.
The next important Fifth Circuit case to consider what kind of checkpoint merits functional equivalency status was United States v. Alvarez-Gonzalez, 542 F.2d 226 (5th Cir.1976) (Alvarez-Gonzalez I), a case concerned with a checkpoint at La Gloria, Texas. The Alvarez-Gonzalez I court adopted a tripartite test for determining functional equivalency: (1) the ratio between international and domestic traffic passing through such checkpoints must not be disproportionately domestic; (2) it must be a permanent checkpoint; and (3) as to international traffic, it must approximate the effect of one physically located at the border. Id. at 229. The test prescribed in Alvarez-Gonzalez I appeared to narrow the Hart I test somewhat, by limiting functional equivalent of the border checkpoints to ones interdicting predominantly “international traffic.” On remand, the district court found that the La Gloria checkpoint merited functional equivalency status under the Alvarez-Gonzalez I test, and we affirmed. United States v. Alvarez-Gonzalez, 561 F.2d 620 (5th Cir.1977) (Alvarez-Gonzalez II).
Following the court's earlier remand, the border patrol conducted a survey to assess the ratio of international to domestic traffic passing through the checkpoint. The survey indicated that sixty percent of this traffic was international in origin. Significantly, however, the survey included as “international traffic” vehicles that had originated in the “immediate border area” on the American side. The court defended the use of this measure as follows:
It would make little sense indeed to adopt a definition of “international” for this purpose which excluded those very journeys which evidence and practical experience have demonstrated are most likely to commence with an illegal international border crossing. In such situations, although the vehicle has not crossed the border, its cargo has.
Id. at 623-24.
By adopting a definition of international traffic that included domestic traffic, the Alvarez-Gonzalez II court, like Hart I before it, “struck a balance between the needs of law enforcement and the constitutional rights of residents near the Mexican border.” Id. at 625. The court determined that the Fourth Amendment’s rule of reason allowed the government at the La Gloria checkpoint to conduct “a cursory inspection for alien passengers limited to cavities large enough to contain a human form.” Id. The court specifically noted, however, that a more intrusive search for contraband “could well result in the striking of a different balance in determining a checkpoint’s status as a functional equivalent of the border.” Id.
We returned to the Sierra Blanca checkpoint in 1979 to consider the constitutionality of a search that uncovered 138 pounds of marijuana in the trunk of an MGB sports car. United States v. Luddington, 589 F.2d 236, 237 (5th Cir.), cert. denied, 441 U.S. 936, 99 S.Ct. 2061, 60 L.Ed.2d 666 (1979). Relying on Hart I and Alvarez-Gonzalez II, the Luddington court upheld the constitutionality of the search on the basis of the continuing need to carefully monitor the border area in order to intercept aliens who had recently crossed the border unchecked. The court also observed that the checkpoint only minimally affects domestic traffic, but at the same [857]*857time reiterated the need for a definition of international traffic not limited to traffic which has crossed the border, “since vehicles which remain in this country and await their illegal human cargo are a principal means of alien smuggling.” Id. at 241.
For the first time in Luddington, however, we upheld a search of compartments too small to hide an illegal alien. The border patrol agent there could only open the small MGB trunk a few inches, because of a luggage rack, but far enough to know that no illegal aliens were hidden inside. The agent was able to observe several packages wrapped in plastic, which led him to refer the vehicle to a secondary inspection area where the marijuana was discovered. The authority for the search derived solely from the checkpoint’s status as a border equivalent; probable cause was not raised as an alternative ground to support the search. Although the Luddington court purported to follow the rule of Alvarez-Gonzalez II, it did not comment upon the intrusiveness of the search, which went significantly beyond any of the checkpoint searches previously approved by this court. For the first time in Luddington, therefore, the court invested agents at the Sierra Blanca checkpoint with the same authority to search that agents possess at the nation’s border, based solely on the checkpoint’s designation as a border “equivalent,” but without any independent assessment of the reasonableness of the searches themselves.
Any doubts about the scope of the government’s power to search at the Sierra Blanca checkpoint were answered in United States v. Dreyfus-de Campos, 698 F.2d 227 (5th Cir.1983), where we upheld a search of a shaving kit. The court held, “ ‘[i]t is not required that the underlying facts concerning a particular checkpoint location be proved over and over again in each case arising out of the same checkpoint location, so long as such facts remain unchanged.’ ” Id. at 229 (quoting United States v. Salinas, 611 F.2d 128, 130 (5th Cir.1980)). Finding no evidence to suggest changed circumstances since Luddington, the court upheld the constitutionality of the search. Once again, however, the court did not analyze the justification for the searches being conducted at the Sierra Blanca checkpoint, which fully matched those conducted at the border.
More recently, panels of this court have again upheld the constitutionality of complete searches at the Sierra Blanca checkpoint on the basis of its status as a border equivalent. United States v. Oyarzun, 760 F.2d 570, 576 (5th Cir.1985); United States v. Jackson, 807 F.2d 1185, 1190 (5th Cir.1986). As the panel opinion in the present case flatly stated: “The established law is clear. Searches at the Sierra Blanca checkpoint are the functional equivalent of border searches and meet the Fourth Amendment requirement of reasonableness.” Id.
II
The Fourth Amendment and Functional Equivalents of The Border
As the cases described in the previous section indicate, this circuit’s designation “functional equivalent of the border” has been founded on the Fourth Amendment’s “rule of reason,” in light of the “staggering” problem of aliens entering the United States illegally, and with the impossibility of stemming this illegal tide by patrolling the full length of the nation’s expansive southern border with Mexico cited as justification for searches away from the border. However, contrary to the “exigent circumstances” analysis of our cases, the constitutionality of searches conducted at a border equivalent does not depend on a Fourth Amendment analysis. Searches at checkpoints functionally equivalent to the border are premised upon the same principles supporting similar searches at the border itself, Almeida-Sanchez, 413 U.S. at 272, 93 S.Ct. at 2539; and “the ‘border search’ exception is not based on the doctrine of ‘exigent circumstances’ at all.” United States v. Ramsey, 431 U.S. 606, 621, 97 S.Ct. 1972, 1981, 52 L.Ed.2d 617 (1977). In fact, border searches are not “embraced within the prohibition of the [Fourth] [AJmendment.” Id. (quoting Carroll v. [858]*858United States, 267 U.S. 132, 150, 45 S.Ct. 280, 284, 69 L.Ed. 543 (1925)). The constitutional basis for searches at border checkpoints is fundamentally different from the basis for “stops” at checkpoints in the interior of the United States. Our cases have erred in confusing the two.
In Ramsey, (now Chief) Justice Rehnquist, writing for the Court, explained the special analysis for border searches as follows:
Border searches, then, from before the adoption of the Fourth Amendment, have been considered to be “reasonable” by the single fact that the person or item in question had entered into our country from outside. There has never been any additional requirement that the reasonableness of a border search depended on the existence of probable cause. This longstanding recognition that searches at our borders without probable cause and without a warrant are nonetheless “reasonable” has a history as old as the Fourth Amendment itself.
431 U.S. at 619, 97 S.Ct. at 1980 (emphasis added). See also United States v. Montoya de Hernandez, 473 U.S. 531, 554-55, 105 S.Ct. 3304, 3318, 87 L.Ed.2d 381 (1985) (Brennan, J., dissenting) (“the power of Congress to authorize wide-ranging detentions and searches [at the border] for purposes of immigration and customs control is unquestioned”) (emphasis in original).
The Supreme Court’s approval of searches at checkpoints functionally equivalent to the border is based on this same principle, the only difference being that through necessity or convenience border searches are condoned away from the border. It is the single fact that the individual or item has entered this nation from outside that justifies the search. Montoya de Hernandez, 473 U.S. at 537-38, 105 S.Ct. at 3309. The Court in Carroll v. United States, 267 U.S. at 154, 45 S.Ct. at 285, explained why such border searches are reasonable:
Travelers may be so stopped in crossing an international boundary because of national self-protection reasonably requiring one entering the country to identify himself as entitled to come in, and his belongings as effects which may be lawfully brought in. But those lawfully within the country, entitled to use the public highways, have a right to free passage without interruption or search unless there is known to a competent official authorized to search, probable cause for believing that their vehicles are carrying contraband or illegal merchandise.
By including domestic traffic in our definition of international traffic,4 our cases have perverted the limiting principle inherent in the border search exception. The government’s power to stop and examine vehicles crossing into this country derives solely from the sovereign’s right of self-protection. Ramsey, 431 U.S. at 616, 97 S.Ct. at 1978; see generally Note, Functional Equivalents of The Border, Sovereignty, and The Fourth Amendment, 52 U.Chi.L.Rev. 1119 (1985). Motorists lawfully travelling on this nation’s roadways [859]*859are clothed with Fourth Amendment protection from arbitrary government interference. Therefore, only searches of persons or effects that have crossed the border may be deemed functionally equivalent to border searches and hence be excepted from the Fourth Amendment’s compass. This limitation is consistent with the interpretation other circuits have given the functional equivalency notion. See e.g., United States v. Garcia, 672 F.2d 1349, 1365 (11th Cir.1982) (Functional equivalent of the border “searches are truly border searches because their sole justification is the fact that the border has been crossed.”); accord United States v. Sugrim, 732 F.2d 25, 29 (2d Cir.1984); United States v. Caminos, 770 F.2d 361, 364 (3d Cir.1985); United States v. Bilir, 592 F.2d 735, 742 n. 11 (4th Cir.1979); United States v. One (1) 1966 Beechcraft Baron, No. N242BS, 788 F.2d 384, 388 (6th Cir.1986); United States v. Carter, 592 F.2d 402, 404 (7th Cir.1979); United States v. Udofot, 711 F.2d 831, 839 (8th Cir.1983); United States v. Whiting, 781 F.2d 692, 695 (9th Cir.1986); United States v. Mayer, 818 F.2d 725, 727 (10th Cir.1987); Jasinski v. Adams, 781 F.2d 843, 846 (11th Cir.1986). In fact, cases in this circuit considering functional equivalent of the border searches as they pertain to individual searches of persons or effects also hold that an actual border crossing must have occurred to justify a search.
In United States v. Amuny, 767 F.2d 1113 (5th Cir.1985), for example, customs agents electronically tracked a plane they suspected of being used to smuggle drugs as it left Galveston, but subsequently lost it around Palacios, Texas, a town on the coast of the Gulf of Mexico. The next day agents picked up the plane around Palacios, and tracked it as it returned northward to Galveston. When the plane landed, customs agents searched it and found marijuana on board. At the suppression hearing, the officers explained that they based the search on their “suspicion” that the plane had crossed the border. The panel held that suspicion alone could not support the search: “To justify a search at the functional equivalent of the border, agents must demonstrate to a ‘reasonable certainty’ that the vehicle has, in fact, crossed the international border.” Id. at 1123 (emphasis added); see also United States v. Niver, 689 F.2d 520, 526 (5th Cir.1982); United States v. Barbin, 743 F.2d 256, 261 (5th Cir.1984); United States v. Melendez-Gonzalez, 727 F.2d 407, 411 (5th Cir.1984). The mere opportunity to have crossed the border is not enough. Amuny, 767 F.2d at 1124; see United States v. Brennan, 538 F.2d 711, 715 (5th Cir.1976), cert. denied, 429 U.S. 1092, 97 S.Ct. 1104, 51 L.Ed.2d 538 (1977). The “reasonable certainty” test “require[s] something more than a showing of probable cause but something less than proof beyond a reasonable doubt” of a border crossing. Amuny, 767 F.2d at 1123; Niver, 689 F.2d at 526.
Although our checkpoint cases developed separately from the Amuny line of cases, the notion of border equivalence should be the same whether referring to searches of aircraft landing after crossing the border or at checkpoints located near the border, since their “reasonableness” emanates from the same source: the sovereign’s historical right to inspect persons and effects entering the country. Indeed, searches of aircraft that have crossed the border and searches at checkpoints near the border were the very examples Justice Stewart cited in Almeida-Sanchez as possible border equivalents. Significantly, however, while he found the search of an “airplane arriving at a St. Louis airport after a nonstop flight from Mexico [to] clearly be the functional equivalent of a border search,” he observed that searches conducted at checkpoints on roads “that extend from the border [only] might be functional equivalents of border searches.” Almeida-Sanchez, 413 U.S. at 272-73, 93 S.Ct. at 2539 (emphasis added). The degree of certainty Justice Stewart expressed in the two examples derives from the relative certainty that a border crossing has occurred. Whereas a nonstop flight from Mexico has certainly crossed the border, vehicles travelling on roads leading away from the border may not have done so. Whether a checkpoint merits functional [860]*860equivalency status, therefore, depends entirely on the nature of the traffic passing through it. To justify searches at checkpoints labeled the functional equivalent of the border the government must demonstrate with “reasonable certainty” that the traffic passing through the checkpoint is “international” in character. See United States v. Mayer, 818 F.2d 725, 727 (10th Cir.1987); United States v. One (1) 1966 Beechcraft Baron, No. N242BS, 788 F.2d 384 (6th Cir.1986). In practical terms, this test means that border equivalent checkpoints intercept no more than a negligible number of domestic travelers. The government concedes that the Sierra Blanca checkpoint, and all similarly situated checkpoints, do not meet this test. We turn, therefore, to consider whether the searches now conducted at these checkpoints, though not border equivalent searches, may nevertheless be reasonable under the Fourth Amendment because of the public interests at stake.
Ill
The Fourth Amendment and Permanent Checkpoints
As we noted above, and as the Supreme Court has repeatedly emphasized, the constitutionality of a particular government intrusion depends on its “reasonableness.” See e.g., Montoya de Hernandez, 473 U.S. at 536-38, 105 S.Ct. at 3308-09; United States v. Villamonte-Marquez, 462 U.S. 579, 588, 103 S.Ct. 2573, 2579, 77 L.Ed.2d 22 (1983). “Thus, the permissibility of a particular law enforcement practice is judged by balancing its intrusion on the individual’s Fourth Amendment interests against its promotion of legitimate governmental interests.” Delaware v. Prouse, 440 U.S. 648, 654, 99 S.Ct. 1391, 1396, 59 L.Ed.2d 660 (1979). However, the Court has already conducted the necessary balancing test in the present context, and has discriminatingly calibrated the reasonable level of intrusiveness in light of the public interests at stake in these cases.
The government stresses, and our previous cases have recognized, the very serious problem of illegal aliens streaming into the United States at unmonitored points along the border. See, e.g., Alvarez-Gonzalez II, 561 F.2d at 625 (“The magnitude of the problem of aliens illegally entering or remaining in the United States is staggering.”). Yet the public interest in the present case is the same as that raised in all of the Supreme Court’s border control cases: the “formidable law enforcement problem[]” of “[interdicting the flow of illegal entrants from Mexico.” United States v. Martinez-Fuerte, 428 U.S. 543, 552, 96 S.Ct. 3074, 3080, 49 L.Ed.2d 1116 (1976); see also Almeida-Sanchez, 413 U.S. at 273, 93 S.Ct. at 2540; United States v. Brignoni-Ponce, 422 U.S. 873, 878-79, 95 S.Ct. 2574, 2579, 45 L.Ed.2d 607 (1975); United States v. Ortiz, 422 U.S. 891, 892, 95 S.Ct. 2585, 2586, 45 L.Ed.2d 623 (1975). In Brignoni-Ponce, the Court summarized the problem as follows:
[T]he public interest demands effective measures to prevent the illegal entry of aliens at the Mexican border.... [Tjhese aliens create significant economic and social problems, competing with citizens and legal resident aliens for jobs, and generating extra demand for social services. The aliens themselves are vulnerable to exploitation because they cannot complain of substandard working conditions without risking deportation.
422 U.S. at 878-79, 95 S.Ct. at 2579. Despite the similarity between this case and the several Supreme Court checkpoint cases, the government urges this court to approve searches at permanent checkpoints far more intrusive than any so far sanctioned by the High Court.
In a case nearly indistinguishable from the present one, the Court in Ortiz considered the question “whether vehicle searches at [permanent] traffic checkpoints ... must be based on probable cause.” 422 U.S. at 892, 95 S.Ct. at 2586. The checkpoint in Ortiz was located on the principal highway connecting San Diego and Los Angeles, approximately 62 air miles and 66 road miles north of the border. A routine immigration inspection at the checkpoint uncovered three illegal aliens secreted in the trunk of the defendant’s [861]*861car. The government argued that the checkpoint’s permanency distinguished its level of intrusiveness from the roving patrols found unreasonably intrusive in Almeida-Sanchez. 413 U.S. at 274, 93 S.Ct. at 2540. In particular, at permanent checkpoints motorists would not be frightened or annoyed by brief inspections, and officers had little discretion in deciding who to stop. The Court rejected these assertions, finding that “[t]he greater regularity attending the stop does not mitigate the invasion of privacy that a search entails.” Id. 422 U.S. at 895, 95 S.Ct. at 2588. The Ortiz Court concluded, “[t]o protect that privacy from official arbitrariness, the Court always has regarded probable cause as the minimum requirement for a lawful search.” Id. at 896, 95 S.Ct. at 2588.
The public interests cited by the government in this case are identical to the ones noted by the Supreme Court in Ortiz. The basic operation of the Sierra Blanca checkpoint, and especially its degree of intrusiveness, is the same as well. The only possible distinction may be that Sierra Blanca stands fourteen air miles from the Mexican border in Texas, whereas the San Clemente checkpoint reviewed in Ortiz was located sixty-two air miles from the Mexican border in California. This distinction, however, does not justify a different result. Enforcement officials at the Sierra Blanca checkpoint have been granted nearly free license. They exercise the power to choose which cars to search, without any obligation to articulate any reason for their choice. Such unbounded discretion creates the potential for significant abuse, since any vehicle or person may be stopped and searched for any reason, or no reason. Ortiz, 422 U.S. at 896, 95 S.Ct. at 2588.
In several early cases we suggested that allowing “a cursory inspection for alien passengers limited to cavities large enough to contain a human form” might strike a reasonable balance “between the needs of law enforcement and the constitutional rights of residents near the Mexican border.” Alvarez-Gonzalez II, 561 F.2d at 625. Yet the very search found unconstitutional in Ortiz was a “routine immigration” search of a vehicle’s trunk. Thus, the Court has already passed judgment upon the inspections we contemplated in Alvarez-Gonzalez, and found them to be unreasonable. However, the Ortiz Court left open the question whether less intrusive checkpoint stops, “stops for the purpose of inquiring about citizenship,” could pass constitutional muster. 422 U.S. at 898-99, 95 S.Ct. at 2589-90 (Rehnquist, J., concurring).
One year after Ortiz, the Court examined the constitutionality of checkpoint stops less intrusive than the immigration searches declared unconstitutional in Ortiz. In Martinez-Fuerte, the Court approved the brief detention of vehicles at permanent checkpoints so that occupants could be questioned regarding their right to be in the United States. 428 U.S. at 558, 96 S.Ct. at 3083. The Court also found referrals to secondary inspection areas for further questioning constitutional. Id. The Court explained that, although creating some inconvenience to the motoring public, a brief detention did not impermissibly intrude on individual privacy interests. The permanent nature of the checkpoint lessens the possibility that motorists will be taken by surprise, and officers at permanent checkpoints do not exercise the broad discretion found troubling in roving patrol stops. See Brignoni-Ponce, 422 U.S. at 882-83, 95 S.Ct. at 2580-81. Moreover, the intrusiveness of the stop is strictly limited, since “[njeither the vehicle nor its occupants are searched, and visual inspection of the vehicle is limited to what can be seen without a search.” Martinez-Fuerte, 428 U.S. at 558, 96 S.Ct. at 3083.
Although cursory inspections of automobile trunks are less intrusive than complete searches, they are nonetheless searches under the Fourth Amendment. The Supreme Court has repeatedly emphasized that “[t]he principal protection of Fourth Amendment rights at checkpoints lies in appropriate limitations on the scope of the stop.” Martinez-Fuerte, 428 U.S. at 566-67, 96 S.Ct. at 3087; see Terry v. Ohio, 392 U.S. 1, 24-27, 88 S.Ct. 1868, 1881-83, 20 L.Ed.2d 889 (1968); Brignoni-Ponce, 422 U.S. at 881-82, 95 S.Ct. at 2580-81. In [862]*862Martinez-Fuerte, the Court strictly limited the scope of stops at permanent checkpoints, specifically holding that “checkpoint searches are constitutional only if justified by consent or probable cause to search [and that] ‘[a]ny further detention must be based on consent or probable cause.' ” 428 U.S. at 567, 96 S.Ct. at 3087 (quoting Brignoni-Ponce, 422 U.S. at 882, 95 S.Ct. at 2580) (emphasis added). Indeed, in every one of its many checkpoint and roving patrol cases, the Supreme Court has restricted the level of government intrusion to brief detentions only long enough to ask questions and check citizenship status. See e.g., Villamonte-Marquez, 462 U.S. at 592, 103 S.Ct. at 2581 (holding that random stops of vessels are reasonable because they “involve[ ] only a brief detention where officials come on board, visit public areas of the vessel, and inspect documents”). The Court has thus demarcated the boundary of privacy that officials at checkpoints cannot intrude without reason.
We might question whether limiting officers at permanent checkpoints to brief questioning of motorists frustrates law enforcement efforts. Checkpoint agents may stop and query motorists about their citizenship, and also request production of documents evidencing a right to be in the United States. Martinez-Fuerte, 428 U.S. at 559, 96 S.Ct. at 3083. Moreover, checkpoint agents may selectively refer motorists to secondary inspection areas for additional questioning without articulating any reason for doing so. Id. at 563-64, 96 S.Ct. at 3085. As demonstrated by their widespread use, these procedures provide an effective law enforcement tool in checking the tide of illegal immigration. See id. at 562 n. 15, 96 S.Ct. at 3085 n. 15. In practice, brief detentions at checkpoints increase agents’ ability to identify illegal aliens by affording them a greater opportunity to scrutinize individual vehicles and their occupants, and thereby develop probable cause or obtain consent to support a search.
If removing the government’s plenary power to search at permanent checkpoints does actually diminish effective enforcement of the immigration laws, the Fourth Amendment balance between the government intrusion and the individual’s privacy right under these circumstances has been struck by the Supreme Court in Martinez-Fuerte, and that is dispositive of the issue for us. Nonetheless, on several occasions the Court has noted the possible availability of an alternative, the “area warrant,” that might allow the striking of a slightly different balance between the government’s legitimate need to control the nation’s border and motorists’ protected right to travel in areas near the border without interference. We will therefore consider this alternative.
IV
“Area Warrants” and Permanent Checkpoints
In his concurring opinion in Almeida-Sanchez, Justice Powell compared the illegal alien problem along the border to the situation presented in Camara v. Municipal Court, 387 U.S. 523, 87 S.Ct. 1727, 18 L.Ed.2d 930 (1967), involving housing code violations. The Camara Court held that administrative inspections of individual structures could be conducted on the basis of general knowledge about the area as a whole rather than specific knowledge concerning the condition of the particular building inspected. See generally Kress & Iannelli, Administrative Search and Seizure: Whither The Warrant?, 31 VÍ11.L. Rev. 705, 714-17 (1986). However, these “area inspections” had to be accompanied by a warrant unless a traditional exception, such as exigent circumstances, existed. Camara, 387 U.S. at 539, 87 S.Ct. at 1736. The Court explained that the Fourth Amendment’s guiding principle of reasonableness required the striking of a careful balance between the need for the search and the limited invasion of privacy occasioned by administrative searches accompanied by a warrant. Id. at 535-37, 87 S.Ct. at 1734-35. Justice Powell, and at least four other members of the Almeida-San-[863]*863chez Court,5 believed that the illegal alien problem in the border region presented an analogous situation to that in Camara, and one which might allow limited automobile searches by border patrol agents when supported by general knowledge of the area in question and an “area warrant.” See generally Note, Area Search Warrants in Border Zones: Almeida-Sanchez and Camara, 84 Yale L.J. 355, 360-72 (1974).
In Camara, the Court cited three factors for its conclusion that administrative area inspections of property were reasonable under the Fourth Amendment. These factors included a “ ‘long history of judicial and public acceptance,’ ” the lack of other means to vindicate the public interest at stake, and the “limited invasion of privacy occasioned by administrative inspections which are ‘neither personal in nature nor aimed at the discovery of evidence of crime.’ ” Almeida-Sanchez, 413 U.S. at 278, 93 S.Ct. at 2542 (Powell, J., concurring) (quoting Camara, 387 U.S. at 537, 87 S.Ct. at 1735). Justice Powell found these three factors similarly applicable to roving patrols for illegal aliens in the border region. First, up until Almeida-Sanchez, courts had consistently upheld roving automobile searches for aliens in border areas. Id. Second, no other effective method exists to ferret out illegal aliens as they move from the border into the interior of the United States. Id. And third, these searches resemble administrative searches in that their function “is simply to locate those who are illegally here and to deport them,” not to uncover evidence for prosecutions. Id. Justice Powell identified two additional factors to reinforce his analysis. Foremost, these patrols are limited strictly to the border region where the high incidence of illegal alien traffic justifies the limited government intrusion. Id. at 279, 93 S.Ct. at 2542. Secondly, searches of automobiles have traditionally been viewed as less intrusive than searches of persons or buildings. Id. Although Justice Powell suggested the use of “area warrants” to alleviate the constitutional deficiencies of roving border patrols, the concept applies equally to permanent checkpoints. See Ortiz, 422 U.S. at 897 n. 3, 95 S.Ct. at 2589 n. 3.
It is evident that the factors listed by Justice Powell as supporting border area searches of automobiles also formed the basis for the finding in our earlier cases that these searches were “reasonable” as “functional equivalent of the border searches.” See Jackson, 807 F.2d at 1190; Alvarez-Gonzalez II, 561 F.2d at 622-26. However, unlike Justice Powell’s proposal, our checkpoint cases failed to place effective restrictions on the power to search in the vicinity of the border. The functional equivalence label empowered agents at permanent checkpoints to fully search vehicles without articulating any reason for the search, and dependent only on the discretion of those charged with the law enforcement function. The pressure to discharge the law enforcement function too easily leads to the adoption of a narrow view of constitutionally protected rights. See United States v. United States District Court, 407 U.S. 297, 317, 92 S.Ct. 2125, 2136, 32 L.Ed.2d 752 (1972). Sensitive constitutional determinations ordinarily require the more dispassionate perspective offered by magistrates. By extending the Court’s Camara-analysis to the border area, however, the power to search becomes subject to judicial oversight through the requirement that border area searches be accompanied by an “area warrant.”
Only when “the burden of obtaining a warrant is likely to frustrate the governmental purpose behind the search” should [864]*864the warrant requirement be dispensed with. Camara, 387 U.S. at 533, 87 S.Ct. at 1733. Nothing in the area warrant concept itself should cause such frustration, however. The government has acknowledged that the infiltration patterns of illegal aliens is well known, and, particularly east of Sierra Blanca, their routes into the interior of the United States are relatively few, thus making permanent checkpoints extremely effective. Since illegal immigration patterns are discoverable prior to the establishment of a checkpoint, and the geography of the area remains unchanged over time, judicial review of the reasonableness of proposed procedures should not ordinarily frustrate government action.
Justice Powell identified four factors bearing on the reasonableness of an area warrant in a given case:
(i) the frequency with which aliens illegally in the country are known or reasonably believed to be transported within a particular area; (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, 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.
Almeida-Sanchez, 413 U.S. at 283-84, 93 5.Ct. at 2545. We consider only generally the application of these four factors to the permanent checkpoint at Sierra Blanca.
The first factor concerns the volume of illegal alien traffic in a particular area. The government has convincingly demonstrated the significant numbers of illegal aliens that consider I — 10 through Sierra Blanca their highway to the interior of the United States. However, unlike the other three factors, this one has the potential to change over time. As the United States increases enforcement of the immigration laws, and passes new measures making the trek north less attractive for those traveling illegally, the absolute number of illegal aliens may be expected to decrease accordingly.6 Because the facts may change, the government should demonstrate that illegal immigration remains significantly great in the area in question to support renewal of the area warrant.
The second and third factors relate to the geographic characteristics of the area where the searches will take place. The geography surrounding Sierra Blanca, and in particular the stretch of roadway between El Paso and the checkpoint, strongly supports the propriety of the selected location. Leaving El Paso, the interstate runs parallel to the border for approximately eighty miles, at times passing as close as 200 yards, before turning northward toward the checkpoint, which is situated just fourteen air-miles from the border. All along this distance illegal aliens can steal across the border by swimming, wading and, in some areas, even walking across the Rio Grande River without ever meeting a border patrol agent. See Hart I, 506 F.2d at 897; Luddington, 589 F.2d at 240. Moreover, illegal aliens traveling north or east have little choice but to pass through the Sierra Blanca checkpoint on 1-10. To the north of I — 10 lies a remote region with few roads, all of which are monitored by the border patrol, and to the east I — 10 cuts through the Quitman Mountains, effectively creating a funnel through which virtually all traffic must pass. The special nature of this area, therefore, makes placement of the checkpoint at Sierra Blanca particularly effective.
The final factor suggested by Justice Powell for consideration is the degree to which the search interferes with the lawful travel of innocent persons. The magnitude of the intrusion should be assessed in several ways. First, when reviewing a request for an area warrant, magistrates should carefully compare the volume of [865]*865illegal alien traffic with the volume of lawful domestic traffic in the area in question. This comparison may be based on general information known about the area as a whole. However, when the government seeks to renew an area warrant, it should be required to convince the magistrate of the efficacy of the checkpoint searches, either because the operation has impeded the illegal traffic or apprehended a sufficient number of illegal aliens.
A second and more important measure of intrusiveness is the scope of the search. The original justification for border area searches comes from the analogy to administrative searches, i.e., searches “neither personal in nature nor aimed at the discovery of evidence of crime.” Camara, 387 U.S. at 537, 87 S.Ct. at 1735. Searches aimed at discovering evidence of crime tend to be more intrusive than administrative searches. See, e.g., Ingraham v. Wright, 430 U.S. 651, 673-74 n. 42, 97 S.Ct. 1401, 1413-14 n. 42, 51 L.Ed.2d 711 (1977); see generally Note, The Civil and Criminal Methodologies of the Fourth Amendment, 93 Yale L.J. 1127, 1135-38 (1984). Moreover, the scope of the search should be strictly confined to the purposes justifying it. See Terry v. Ohio, 392 U.S. at 25-26, 88 S.Ct. at 1882 (“A search ... must ... be strictly circumscribed by the exigencies which justify its initiation.”). Therefore, when the only government interest asserted is illegal immigration, the scope of border area searches must be limited to compartments large enough to secrete a person. We decline to comment on the issue of area warrants to sanction searches aimed exclusively at uncovering evidence of crime.
Again, we note that we are not entirely convinced that Martinez-Fuerte-type checkpoint operations fail to give the government an adequate mechanism by which to identify vehicles carrying illegal aliens. The brief detention of vehicles with observation and questions by an experienced officer provides a substantial enforcement tool. The government bears the burden to demonstrate not only that the public interest makes cursory inspections reasonable; it must show that less intrusive methods cannot be effective enough to meet the public interests at stake. As we read a map in this record, there is a checkpoint located on I — 10 west of El Paso and within New Mexico. Because New Mexico lies in the Tenth Circuit, the intrusion there is undoubtedly patterned to Martinez-Fuerte. A comparison of the consequences of that checkpoint, as well as those near the Mexican border but in the Ninth Circuit, would be useful.
V
Good Faith Reliance on Fifth Circuit Precedent
Appellants urge this court to apply the exclusionary rule and suppress the evidence discovered during the searches we now deem illegal. Weeks v. United States, 232 U.S. 383, 34 S.Ct. 341, 58 L.Ed. 652 (1914); Mapp v. Ohio, 367 U.S. 643, 81 S.Ct. 1684, 6 L.Ed.2d 1081 (1961). The primary purpose of the exclusionary rule “is to deter future unlawful police conduct and thereby effectuate the guarantee of the Fourth Amendment against unreasonable searches and seizures.” United States v. Calandra, 414 U.S. 338, 347, 94 S.Ct. 613, 619-20, 38 L.Ed.2d 561 (1974). In United States v. Leon, 468 U.S. 897, 920-21, 104 S.Ct. 3405, 3419, 82 L.Ed.2d 677 (1984), however, the Court declined to apply the exclusionary rule to cases where an officer, acting in “objective good faith,” had relied on a search warrant. Under such circumstances, the Court reasoned, the exclusionary rule would not deter police misconduct.
The Leon Court believed there was no sound reason for extending the exclusionary rule to deter misconduct on the part of judicial officers responsible for issuing search warrants. Id. at 915-18, 104 S.Ct. at 3417-18; see also Illinois v. Krull, — U.S. -, 107 S.Ct. 1160, 1166, 94 L.Ed.2d 364 (1987) (holding that the exclusionary rule does not apply where an officer acted in objectively reasonable reliance on a statute). The Court explained that there was “no evidence suggesting that judges and magistrates are inclined to ignore or sub[866]*866vert the Fourth Amendment or that lawlessness among these actors requires application of the extreme sanction of exclusion.” Id. 468 U.S. at 916, 104 S.Ct. at 3417. Moreover, exclusion would have no deterrent effect, since “[¡judges and magistrates are not adjuncts to the law enforcement team; as neutral judicial officers, they have no stake in the outcome of particular criminal prosecutions.” Id. at 917, 104 S.Ct. at 3417. The reasoning of Leon fully applies to the case at hand. Panels of this court have upheld searches at the Sierra Blanca checkpoint numerous times, and appellants do not suggest that this court is “inclined to ignore or subvert the Fourth Amendment.” Id. at 916,104 S.Ct. at 3417. Under these circumstances,
“[ejxcluding the evidence will not further the ends of the exclusionary rule in any appreciable way; for it is painfully apparent that ... the officer is acting as a reasonable officer would and should act in similar circumstances. Excluding the evidence can in no way affect his future conduct unless it is to make him less willing to do his duty.”
Id. at 920, 104 S.Ct. at 3420 (quoting Stone v. Powell, 428 U.S. 465, 540, 96 S.Ct. 3037, 3073, 49 L.Ed.2d 1067 (1967) (White, J., dissenting)).
It follows from this holding that in other cases the exclusionary rule should not be applied to searches which relied on Fifth Circuit law prior to the change of that law on the date of the delivery of this opinion.
The appellants’ convictions are AFFIRMED.