ORDER AND JUDGMENT*
TERRENCE L. O’BRIEN, Circuit Judge.
Driving north from the border in the remote “bootheel” section of southwestern New Mexico, Luis Edgar Montes-Ramos was pulled over by a deputy sheriff because his temporary registration tag was not properly affixed to his vehicle or legible. While waiting for Montes-Ramos to produce his driver’s license, the deputy noticed a blanket in the backseat, covering what appeared to be large items. He saw a five-inch circular section of burlap protruding from underneath the blanket. Based on his observation of burlap, his law enforcement experience, and the location of the stop (along a known drug smuggling route), the deputy suspected Montes-Ramos was trafficking marijuana. To con[385] firm his suspicion, he leaned his head into the open window very slightly and sniffed. He smelled marijuana and arrested Montes-Ramos. At the police station, 96 kilograms of marijuana were found in the vehicle. Montes-Ramos appeals from a partial denial of his motion to suppress. Even though the deputy’s minimal intrusion into the vehicle to effectuate the sniff was reasonable under the circumstances, we are obliged to reverse.1
I. BACKGROUND
The facts are not in dispute. Around 11:00 a.m. on February 8, 2006, MontesRamos was driving northbound on New Mexico Highway 80, approximately forty miles north of the border and thirty miles south of Lordsburg, New Mexico.2 Hidalgo County Sheriff’s Deputy Robert Rodriguez was in his patrol car on the shoulder of the southbound side of Highway 80, checking traffic by radar. Rodriguez observed a gold sedan traveling northbound with no license plate; it had instead a piece of paper where the license plate is generally placed. The paper was “flapping in the wind” and was not legible. (R. Vol. Ill at 22.) Rodriguez pulled onto the highway, made a U-turn, and signaled for the driver of the gold sedan — Montes-Ramos — to pull over. When Montes-Ramos pulled over, Rodriguez approached the vehicle on the passenger side. At that point, Rodriguez realized the piece of paper appeared to be a valid Arizona temporary registration tag. However, instead of being affixed inside the back rear window, as normally required by New Mexico law, the tag was encased in a clear plastic envelope, only the top of which was attached to the ear’s license plate holder. The car’s windows were neither tinted nor dirty, and the tag would have been clearly visible if affixed to the inside rear window.
Though he did not intend to issue a ticket, Rodriguez advised Montes-Ramos in Spanish that his tag was placed in the wrong location and asked him to produce his driver’s license. While Montes-Ramos was looking for his license, Rodriguez observed some large items in the backseat, covered by a leopard-print blanket. A five-inch circular section of burlap was visible underneath the blanket. At the hearing on Montes-Ramos’ motion to suppress, Deputy Rodriguez testified “[wjhat [he] observed was consistent with the transportation of illegal contraband into the United States.” (Id. at 14.) He explained drugs are often bundled into tight bricks and wrapped with burlap cloth. When asked whether the bundles he observed “appealed] consistent with burlap packaging of produce like onions or chile,” he answered: “No.” (Id. at 47.) He testified ■that during his almost seventeen years in law enforcement, he had been involved in approximately “one dozen” drug-related investigations, of which “[approximately two” involved the seizure of marijuana packaged in burlap.3 (Id. at 15.)
To confirm his suspicion that MontesRamos was transporting marijuana, Deputy Rodriguez “placed [his] nose — [his] face inside the [front passenger-side] door approximately two inches.” (Id. at 16.) The sole purpose of the sniff was to determine whether there was marijuana in the backseat. After leaning into the car, Rodri[386] guez detected a strong odor of marijuana. He drew his pistol, ordered Montes-Ramos out of the vehicle, handcuffed him, and placed him under arrest. Prior to being read his Miranda4 rights, MontesRamos admitted he was transporting marijuana. While waiting for backup to arrive, Rodriguez removed the blanket from the backseat, pierced one of the bundles, and observed a green leafy substance consistent with marijuana. At the station, a complete search of the vehicle revealed five burlap bags containing 96 kilograms (approximately 211 pounds) of marijuana.
Montes-Ramos was indicted with possession with intent to distribute fifty kilograms and more of marijuana in violation of 21 U.S.C. §§ 841(a)(1), (b)(1)(C) and 18 U.S.C. § 2. He moved to suppress the evidence found in the vehicle and the statements he made to the police. The district court granted the motion as to the roadside statement because Montes-Ramos made it prior to being advised per the requirements of Miranda. The court denied the motion as to all other statements and evidence. It concluded the traffic stop was justified at its inception and was not unreasonably broad. The court considered the sniff to be a search, but held it did not violate the Fourth Amendment because it was supported by reasonable and articulable suspicion and officer safety. MontesRamos pled guilty to the indictment, reserving the right to appeal from the suppression decision. He was sentenced to 21 months imprisonment.5
II. DISCUSSION
“When reviewing the denial of a motion to suppress, we view the evidence in the light most favorable to the government, accept the district court’s findings of fact unless clearly erroneous, and review de novo the ultimate determination of reasonableness under the Fourth Amendment.” United States v. Katoa, 379 F.3d 1203, 1205 (10th Cir.2004).
A. The Stop
The Fourth Amendment protects “[t]he right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures____” U.S. Const, amend. IV. “A routine traffic stop is a ‘seizure’ within the meaning of the Fourth Amendment....” United States v. Ramirez, 479 F.3d 1229, 1243 (10th Cir.2007) (citation omitted), cert. denied, — U.S. -, 128 S.Ct. 1074, 169 L.Ed.2d 817 (2008). “[A] traffic stop is valid under the Fourth Amendment if the stop is based on an observed traffic violation or if the police officer has reasonable articulable suspicion that a traffic or equipment violation has occurred or is occurring.” United States v. Botero-Ospina, 71 F.3d 783, 787 (10th Cir.1995) (en banc).
The initial stop of Montes-Ramos’ vehicle did not violate the Fourth Amendment because Rodriguez observed a violation of N.M. Stat. Ann. § 66-3-18(B), which provides:
A ... temporary registration permit shall be firmly affixed to the inside left [387] rear window of the vehicle to which it is issued, unless such display presents a safety hazard or the ... permit is not visible or readable from that position, in which case, the ... permit shall be displayed in such a manner that it is clearly visible from the rear or left side of the vehicle.
Montes-Ramos was in violation of this statute because his temporary tag was not affixed to the inside left rear window, but was instead displayed outside the vehicle in such a manner that it was not clearly visible from the rear of the vehicle. “[A] vehicle’s apparent failure to display some form of visible license plate/registration tag, temporary or permanent, gives rise to a reasonable suspicion that its driver might be violating any one of the multitude of applicable traffic and equipment regulations of the jurisdiction.” United States v. Edgerton, 438 F.3d 1043, 1048 (10th Cir. 2006) (quotations omitted).
To be reasonable, a traffic stop must not only be “justified at its inception,” the temporary detention associated with the stop must be “reasonably related in scope to the circumstances which justified the interference in the first place.” Botero-Ospina, 71 F.3d at 786 (quotations omitted). Montes-Ramos argues Deputy Rodriguez’s actions violated this second prong, relying on United States v. McSwain, 29 F.3d 558 (10th Cir.1994), and Edgerton. We see it differently.
In MeSwain, a state trooper stopped the defendant’s vehicle “for the sole purpose of ensuring the validity of the vehicle’s temporary registration sticker.” 29 F.3d at 561. As the trooper approached the vehicle on foot, he verified the sticker was valid and had not expired. Id. We held the trooper’s decision to prolong the detention by questioning the defendant and requesting his license and registration “exceeded the scope of the stop’s underlying justification” and therefore violated the Fourth Amendment. Id. In Edgerton, a state trooper stopped the defendant’s vehicle because he could not read the temporary registration tag in the dark. 438 F.3d at 1045. Notably, “the tag was illegible not due to any material within Defendant’s ability to control, but due to external conditions.” Id. at 1050. We held “[o]nce [the trooper] was able to read the Colorado tag and deem it unremarkable, any suspicion that defendant had violated [the Kansas statute relating to the display of license plates] dissipated ... [and the trooper], as a matter of courtesy, should have explained to Defendant the reason for the initial stop and then allowed her to continue on her way without requiring her to produce her license and registration.” Id. at 1051.
The troopers in MeSwain and Edgerton had reasonable suspicion the vehicles they stopped were violating the traffic laws, but their suspicion evaporated when they determined no violations had in fact occurred. Here, by contrast, there was an actual traffic violation — Montes-Ramos’ tag, though valid, was not displayed in accordance with New Mexico law. Thus, Rodriguez’s demand for Montes-Ramos’ license did not exceed the scope of the stop. This case is more analogous to United States v. Concepcion-Ledesma, 447 F.3d 1307 (10th Cir.2006), and United States v. DeGasso, 369 F.3d 1139 (10th Cir.2004). In Concepciortr-Ledesma, we held it was reasonable for the trooper “to issue a written warning, verify [the defendant’s license and registration information, and ask preliminary questions about travel plans” because the trooper saw the defendant’s registration tag displayed in an unlawful manner, even after he approached the vehicle. 447 F.3d at 1314. Similarly, in DeGasso, we upheld a trooper’s detention of the defendant because the trooper [388] observed a continuing violation of state law after stopping the defendant’s vehicle. 869 F.3d at 1141. We distinguished McSwain because “the violation was that the lettering on the license plate was not ‘clearly visible,’ which remained true even after the trooper approached the truck and was able, at that point, to read it.” Id. at 1149. As these cases make clear, an officer does not violate the Fourth Amendment by requesting a driver produce his license after being stopped for a traffic violation.
B. The Sniff
While Rodriguez was waiting for Montes-Ramos to produce his license, he observed suspect objects in the backseat and leaned his head approximately two inches into the car window and sniffed. Montes-Ramos contends the sniff was an unreasonable search; the government contends the sniff was not a search, but if it was a search, it was reasonable. We first consider whether the sniff was a search.
1. Was It A Search?
This Court has not previously considered whether an officer’s intentional act of minimally intruding the air space of a lawfully stopped vehicle for an investigatory purpose constitutes a search within the meaning of the Fourth Amendment. It is not a simple question.
The protections of the Fourth Amendment apply to the interior of automobiles, at least to some extent. In New York v. Class, the Supreme Court held an officer conducted a search within the meaning of the Fourth Amendment when he opened a car door and reached into the interior of the vehicle to move papers obscuring the area of the dashboard where the vehicle identification number (VIN) is typically located. 475 U.S. 106, 108, 115, 106 S.Ct. 960, 89 L.Ed.2d 81 (1986). The Court explained: “While the interior of an automobile is not subject to the same expectations of privacy that exist with respect to one’s home, a car’s interior as a whole is nonetheless subject to Fourth Amendment protection from unreasonable intrusions by the police.” Id. at 114-15, 106 S.Ct. 960. Similarly, in United States v. Ryles, the Fifth Circuit held a trooper’s act of either opening the driver’s side door or sticking his head inside an open window constituted a search because the officer “intruded a space that, under most circumstances, is protected by a legitimate expectation of privacy.”6 988 F.2d 13, 15 (5th Cir.1993); see also United States v. Stone, 866 F.2d 359, 363 (10th Cir.1989) (“People have a reasonable expectation of privacy in the interiors of their automobiles.... ”).
In Kyllo v. United States, the Court remarked: “When the Fourth Amendment was adopted, as now, to ‘search’ meant to look over or through for the purpose of finding something; to explore; to examine by inspection....” 533 U.S. 27, 32 n. 1, 121 S.Ct. 2038, 150 L.Ed.2d 94 (2001) (quotations omitted). Rodriguez’s actions satisfy this definition — he leaned his head into Montes-Ramos’ car to examine by inspection whether the car smelled of marijuana. The fact that the intrusion was minimal does not affect the analysis. In Kyllo, the Court explained: “[Tjhere is certainly no exception to the warrant requirement for the officer who barely cracks open the front door and sees nothing but the nonintimate rug on the vestibule floor.” 533 U.S. at 37, 121 S.Ct. 2038; see also Silverman v. United States, 365 U.S. 505, 512, 81 S.Ct. 679, 5 L.Ed.2d 734 (1961) (refusing to uphold an “actual intrusion into a constitu[389] tionally protected area” despite the fact the intrusion was “by even a fraction of an inch”).7 Over a century ago, Justice Bradley explained: “It may be that it is the obnoxious thing in its mildest and least repulsive form; but illegitimate and unconstitutional practices get their first footing in that way, namely, by silent approaches and slight deviations from legal modes of procedure.” Boyd v. United States, 116 U.S. 616, 635, 6 S.Ct. 524, 29 L.Ed. 746 (1886). If, as Class instructs, the interior airspace of the car is protected, then it must be protected from minimal intrusions as well as flagrant ones.
The only basis we can see for concluding Rodriguez’s sniff was not a search is by analogy to cases involving canine sniffs. In Illinois v. Caballes, the Court held a canine sniff of the exterior of a vehicle during a lawful traffic stop “does not rise to the level of a constitutionally cognizable infringement.” 543 U.S. 405, 409, 125 S.Ct. 834, 160 L.Ed.2d 842 (2005). The Court explained:
The legitimate expectation that information about perfectly lawful activity will remain private is categorically distinguishable from respondent’s hopes or expectations concerning the nondetection of contraband in the trunk of his car. A dog sniff conducted during a concededly lawful traffic stop that reveals no information other than the location of a substance that no individual has any right to possess does not violate the Fourth Amendment.
Id. at 410,125 S.Ct. 834. We are attracted by the reasoning in Caballes; but it is significant that the dog sniff at issue there was conducted on the exterior of the car. While it revealed information about the car’s contents, the dog did not actually intrude into the ear’s protected space.8 Moreover, because a drug dog is trained to alert only to the presence of drugs, its “search” will only disclose information about the presence of certain contraband; it will reveal nothing about other (presumably innocent) smells. Though farfetched, Rodriguez’s sniff could have revealed information about Montes-Ramos’ private, lawful activities — the perfume of a recently departed passenger, a recently consumed lunch, a wet dog — as well as illegal activities — contraband or perhaps a decomposing body.
We conclude a police officer’s intentional act of intruding a vehicle’s air space, even if by only a few inches, constitutes a [390] search within the meaning of the Fourth Amendment. It would be different if Rodriguez had smelled marijuana prior to leaning into Montes-Ramos’ vehicle. Under the plain view doctrine, “a law enforcement officer [may] seize evidence of a crime, without violating the Fourth Amendment, if (1) the officer was lawfully in a position from which the object seized was in plain view, (2) the object’s incriminating character was immediately apparent ... and (3) the officer had a lawful right of access to the object.” United States v. Angelos, 433 F.3d 738, 748 (10th Cir.2006) (quotations omitted). The plain view doctrine is equally applicable to plain smells, such that no search occurs if a police officer detects an odor of illegal drugs, alcohol, chemicals or the like from a location in which he is entitled to be. See id. at 748 (“The plain smell doctrine ... is simply a logical extension of the plain view doctrine ....”) (quotations omitted); United States v. Merryman, 630 F.2d 780, 784 (10th Cir.1980) (“This Circuit has held that the smelling of marijuana by an experienced observer furnishes probable cause for the search.”); see also Kyllo, 533 U.S. at 43-44, 121 S.Ct. 2038 (Stevens, J., dissenting) (“[A]romas that are generated in a kitchen, or in a laboratory or opium den, enter the public domain if and when they leave a building.”). But Rodriguez did not smell marijuana prior to leaning his head into Montes-Ramos’ vehicle. Instead he was suspicious Montes-Ramos might be trafficking drugs and leaned his head in “[f]or assurance.” (R. Vol. Ill at 16.)
2. Was It Reasonable?
Our conclusion that the sniff was a search does not end the analysis because the Fourth Amendment commands only “that searches and seizures be reasonable.” 9 United States v. Montoya de Hernandez, 473 U.S. 531, 537, 105 S.Ct. 3304, 87 L.Ed.2d 381 (1985). The Supreme Court has explained: “What is reasonable depends upon all of the circumstances surrounding the search or seizure and the nature of the search or seizure itself. 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.” Id. (quotations and citation omitted). If this were the Court’s only instruction, we would be inclined to conclude the intrusion here was reasonable. It involved only a slight encroachment into an area that is subject to Fourth Amendment protection only to a limited degree. Montes-Ramos’ vehicle was lawfully stopped at the time of the intrusion and he does not contend the intrusion pro[391] longed the stop (the elapsed time from stop to sniff was less than one minute). Nor does he (or could he) contest the importance and legitimacy of the government interest at stake here — preventing the transportation of illegal narcotics.
But the Supreme Court has also instructed that “warrantless searches are presumptively unconstitutional.” Kyllo, 533 U.S. at 32, 121 S.Ct. 2038. Searches conducted without a warrant are permissible, of course, under certain well-delineated exceptions to the warrant requirement. See Brigham City, Utah v. Stuart, 547 U.S. 398, 403, 126 S.Ct. 1943, 164 L.Ed.2d 650 (2006) (“[BJecause the ultimate touchstone of the Fourth Amendment is ‘reasonableness,’ the warrant requirement is subject to certain exceptions.”). It is not the province of this Court to create a new (or expand an existing) exception to the warrant requirement. Instead, our task is limited to determining whether the government has met its burden of proving the search falls within a recognized exception. See United States v. Maestas, 2 F.3d 1485, 1491 (10th Cir.1993) (“[T]he government has the burden of proving that an exception to the warrant requirement applies.”).
The only apparent exception applicable here is the automobile exception, pursuant to which “[t]he police may search an automobile and the containers within it where they have probable cause to believe contraband or evidence is contained.” Calif. v. Acevedo, 500 U.S. 565, 580, 111 S.Ct. 1982, 114 L.Ed.2d 619 (1991). It is tempting to find probable cause for the sniff and affirm on the basis of our independent review of the record. A legitimate argument could be made that Rodriguez had probable cause for his sniff search.10 But, in spite of a clear opportunity, the government has never made that argument.
In his motion to suppress, Montes-Ramos contended the sniff was unlawful because it was conducted without his consent and without a warrant. In response, the government argued it had probable cause to search the vehicle based, in part, upon the odor of marijuana. But the odor of marijuana cannot factor into the probable cause analysis because Rodriguez did not smell marijuana until after he leaned his head into the vehicle.
At the suppression hearing, the judge was alert to this problem and repeatedly invited the government to focus its attention on whether the sniff was a permissible search. The government uniformly refused the court’s invitation to address the critical issue and instead argued that Rodriguez had, prior to the sniff, acquired enough information “to proceed further with his investigation.” (R. Vol. Ill at 54.) The court stated it was concerned with “how that odor comes to [Rodriguez].” (Id. at 55.) The government responded by citing cases holding a defendant’s rights under the Fourth Amendment are not violated where an officer smells an odor from a location in which he has a right to be. In response, defense counsel argued:
[392] I think when you stick your nose in the car, that’s a search.... If Patrolman Rodriguez walked up to the car and out of the passenger window he smelled marijuana ... we wouldn’t be having this conversation, because it would be an entirely different situation. And I think the cases that [the government] cites talk about situations in which the officer from a position that he was legally entitled to occupy, was able to discern some odor that he recognized as burned or raw marijuana.
(Id. at 59-60.) The government offered rebuttal argument relating to the stop but, again, did not address the operative issue — whether Rodriguez had probable cause for his intrusion into the vehicle to conduct his sniff search.
Ultimately, in spite of its persistent and pertinent questioning, the court abandoned its instincts and accepted the government’s argument, concluding the sniff was permissible even in the absence of probable cause. It explained:
The intrusion was minimal and was substantially outweighed by concerns for officer safety in light of the reasonable suspicion that Montes was engaged in smuggling a large quantity of marijuana. Deputy Rodriguez’s actions were objectively reasonable under the totality of the circumstances and within the range of activities that a police officer may permissibly engage in when he has reasonable suspicion to believe that a vehicle contains narcotics.
(R. Vol. I, Doc. 16 at 9.) It went on to hold that after Rodriguez smelled the marijuana, “there was probable cause to arrest Montes and search the [vehicle].” (Id.)
Even on appeal, the government does not squarely argue the sniff was supported by probable cause.11 It says even if the sniff was a search, it did not violate the Fourth Amendment because it “ ‘stemmed from some probable cause focusing suspicion on the individual affected by the search.’” (Appellee’s Answer Br. at 19-20) (quoting Class, 475 U.S. at 117-18, 106 S.Ct. 960 (1986).)12 It contends that, prior to leaning into Montes-Ramos’ vehicle, Rodriguez directly observed a traffic violation and “observed evidence that led him to believe that Montes’ car contained a load of narcotics.” (Id. at 20.) The government states: “These observations provided a sufficient connection between Montes and the subsequent intrusion and support upholding the search.” (Id.) We are not sure what the government means by “sufficient connection,” but if it is less than probable cause, it is not sufficient.
If Rodriguez reasonably suspected Montes-Ramos was transporting illegal narcotics, he could have detained Montes[393] Ramos and investigated further. He could have asked if Montes-Ramos was transporting narcotics. See United States v. Karam, 496 F.3d 1157, 1161 (10th Cir. 2007). He could have asked for consent to search the vehicle. See United States v. Sanchez, 89 F.3d 715, 719 (10th Cir.1996). He could have stood at the car door, waiting for the smell of marijuana to waft out the window. See Angelos, 433 F.3d at 748. He could have called for a drug dog to sniff the exterior of the vehicle. See United States v. Morales-Zamora, 914 F.2d 200, 203 (10th Cir.1990) (holding a canine sniff on a legitimately detained automobile is not a “search” within the meaning of the Fourth Amendment). And if his suspicion about drug trafficking caused him to fear for his safety, he could have removed Montes-Ramos from his vehicle,13 see Pennsylvania v. Mimms, 434 U.S. 106, 111 n. 6, 98 S.Ct. 330, 54 L.Ed.2d 331 (1977), or looked (perhaps even slightly intruded) into the vehicle to determine whether there were weapons within Montes-Ramos’ reach, see Michigan v. Long, 463 U.S. 1032, 1050, 103 S.Ct. 3469, 77 L.Ed.2d 1201 (1983).14 He could not, however, engage in a warrantless sniff search for drugs — even a minimally intrusive one — unless he had probable cause to believe the vehicle contained contraband or evidence of a crime.
Where, as here, a defendant makes a clear argument in support of a motion to suppress and the government fails to respond to that argument, even when expressly (and repeatedly) invited by the court to do so, the argument is waived. See United States v. Teague, 443 F.3d 1310, 1314 (10th Cir.2006) (“[A] party that has forfeited a right by failing to make a proper objection may obtain relief for plain error; but a party that has waived a right is not entitled to appellate relief.”); see also Singleton v. Wulff, 428 U.S. 106, 120, 96 S.Ct. 2868, 49 L.Ed.2d 826 (1976) (“It is the general rule, of course, that a federal appellate court does not consider an issue not passed upon below.”); Rosewood Servs., Inc. v. Sunflower Diversified Servs., Inc., 413 F.3d 1163, 1167 (10th Cir. 2005) (holding argument not asserted before district court is waived on appeal). This is especially true where the government does not even argue the issue with clarity on appeal.15 See Bronson v. Swen[394] sen, 500 F.3d 1099, 1104 (10th Cir.2007) (“[W]e routinely have declined to consider arguments that are not raised, or are inadequately presented, in an appellant’s opening brief.”); Dubbs v. Head Start, Inc., 336 F.3d 1194, 1202 n. 2 (10th Cir.2003) (where a party does not brief an issue on appeal, the argument is waived).
Accordingly, we REVERSE the district court’s partial denial of Montes-Ramos’ motion to suppress and REMAND for suppression of the fruits of the sniff search and such other necessary proceedings consistent with this Order and Judgment.