Roberts, C.J.
The Fourth Amendment prohibits “unreasonable searches and seizures.” Under this standard, a search or seizure may be permissible even though the justification for the action includes a reasonable factual mistake. An officer might, for example, stop a motorist for traveling alone in a high-occupancy vehicle lane, only to discover upon approaching the car that two children are slumped over asleep in the back seat. The driver has not violated the law, but neither has the officer violated the Fourth Amendment.
But what if the police officer’s reasonable mistake is not one of fact but of law? In this case, an officer stopped a vehicle because one of its two brake lights was out, but a court later determined that a single working brake light was all the law required. The question presented is whether such a mistake of law can nonetheless give rise to the reasonable suspicion necessary to uphold the seizure under the Fourth Amendment. We hold that it can. Because the officer’s mistake about the brake-light law was reasonable, the stop in this case was lawful under the Fourth Amendment.
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A traffic stop for a suspected violation of law is a “seizure” of the occupants of the vehicle and therefore must be conducted in accordance with the Fourth Amendment. Brendlin v. California, 551 U. S. 249, 255–259 (2007). All parties agree that to justify this type of seizure, officers need only “reasonable suspicion”—that is, “a particularized and objective basis for suspecting the particular person stopped” of breaking the law. Prado Navarette v. California, 572 U. S. ___, ___ (2014) (slip op., at 3) (internal quotation marks omitted). The question here is whether reasonable suspicion can rest on a mistaken understanding of the scope of a legal prohibition. We hold that it can.
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But reasonable men make mistakes of law, too, and such mistakes are no less compatible with the concept of reasonable suspicion. Reasonable suspicion arises from the combination of an officer’s understanding of the facts and his understanding of the relevant law. The officer may be reasonably mistaken on either ground. Whether the facts turn out to be not what was thought, or the law turns out to be not what was thought, the result is the same: the facts are outside the scope of the law. There is no reason, under the text of the Fourth Amendment or our precedents, why this same result should be acceptable when reached by way of a reasonable mistake of fact, but not when reached by way of a similarly reasonable mistake of law.
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Contrary to the suggestion of Heien and amici, our decision does not discourage officers from learning the law. The Fourth Amendment tolerates only reasonable mistakes, and those mistakes—whether of fact or of law— must be objectively reasonable. We do not examine the subjective understanding of the particular officer involved. Cf. Whren v. United States, 517 U. S. 806, 813 (1996). And the inquiry is not as forgiving as the one employed in the distinct context of deciding whether an officer is entitled to qualified immunity for a constitutional or statutory violation. Thus, an officer can gain no Fourth Amendment advantage through a sloppy study of the laws he is duty- bound to enforce.
Finally, Heien and amici point to the well-known maxim, “Ignorance of the law is no excuse,” and contend that it is fundamentally unfair to let police officers get away with mistakes of law when the citizenry is accorded no such leeway. Though this argument has a certain rhetorical appeal, it misconceives the implication of the maxim. The true symmetry is this: Just as an individual generally cannot escape criminal liability based on a mistaken understanding of the law, so too the government cannot impose criminal liability based on a mistaken understanding of the law. If the law required two working brake lights, Heien could not escape a ticket by claiming he reasonably thought he needed only one; if the law required only one, Sergeant Darisse could not issue a valid ticket by claiming he reasonably thought drivers needed two. But just because mistakes of law cannot justify either the imposition or the avoidance of criminal liability, it does not follow that they cannot justify an investigatory stop. And Heien is not appealing a brake-light ticket; he is appealing a cocaine-trafficking conviction as to which there is no asserted mistake of fact or law.
ROBERTS, C. J., delivered the opinion of the Court, in which SCALIA, KENNEDY, THOMAS, GINSBURG, BREYER, ALITO, and KAGAN, JJ., joined. KAGAN, J., filed a concurring opinion, in which GINSBURG, J., joined. SOTOMAYOR, J., filed a dissenting opinion.
JUSTICE KAGAN, with whom JUSTICE GINSBURG joins, concurring:
I concur in full in the Court’s opinion, which explains why certain mistakes of law can support the reasonable suspicion needed to stop a vehicle under the Fourth Amendment. In doing so, the Court correctly emphasizes that the “Fourth Amendment tolerates only . . . objectively reasonable” mistakes of law. Ante, at 11. And the Court makes clear that the inquiry into whether an officer’s mistake of law counts as objectively reasonable “is not as forgiving as the one employed in the distinct context of deciding whether an officer is entitled to qualified immunity.” Ibid. I write separately to elaborate briefly on those important limitations.
SOTOMAYOR, J., dissenting:
To my mind, the more administrable approach—and the one more consistent with our precedents and principles—would be to hold that an officer’s mistake of law, no matter how reasonable, cannot support the individualized suspicion necessary to justify a seizure under the Fourth Amendment. I respectfully dissent.