Mr. Justice Black
delivered the opinion of the Court.
Petitioner was convicted in a California state court of selling heroin to a police informer. The conviction rested in part on the introduction in evidence of a small piece of a brown paper sack seized by police without a warrant from the glove compartment of an automobile which police, upon petitioner’s arrest, had impounded and were holding in a garage. The search occurred a week after the arrest of petitioner. Petitioner appealed his conviction to the California District Court of Appeal which, considering itself bound by our holding and opinion in Preston v. United States, 376 U. S. 364, held that the search and seizure violated the Fourth Amendment’s ban of unreasonable searches and seizures. That court went on, however, to determine that this was harmless error under Art. VI, § 4½, of California’s Constitution which provides that judgments should not be set aside or reversed unless the court is of the opinion that the error “resulted in a miscarriage of justice.” 234 Cal. App. 2d 587, 44 Cal. Rptr. 483. The California Supreme Court declined to hear the case. We granted certiorari along with Chapman v. California, ante, p. 18, to consider whether the California harmless-error constitutional provision could' be used in this way to ignore the alleged federal constitutional error. 384 U. S. 904. We have today passed upon the question in Chapman, but do not reach it in this case because we are satisfied that the lower court erroneously decided that our Preston case required that this, search be held- an unreasonable one within the meaning of the Fourth Amendment.
We made it clear in Preston that whether a search and seizure is unreasonable within the meaning of the Fourth Amendment depends upon the facts and circumstances of each case and pointed out, in particular, that searches of cars that are constantly movable may make the search of a car without a warrant a reasonable one although the result might be the opposite in a search of a home, a store, or other fixed piece of property. 376 U. S., at 366-367. In Preston the search was sought to be justified primarily on the ground that it was incidental to and part of a lawful arrest. There we said that “[o]nce an accused is under arrest and in custody, then a search made at another place, without a warrant, is simply not incident to the arrest.” Id., at -367. In the Preston case, it was alternatively argued that the warrantless search, after the arrest was over and while Preston’s car was being held for him by the police, was justified because the officers had probable cause to believe the car was stolen. But the police arrested Preston for vagrancy, not theft, and no claim was made that the police had Authority to hold his car on that charge. The search was therefore to be treated as though his car was in his own or his agent’s possession, safe from intrusions by the police or anyone else. The situation involving petitioner’s car is quite different.
Here, California’s Attorney General concedes that the search was not incident to an arrest. It is argued, however, that the search was reasonable on other grounds. Section 11611 of the California Health & Safety Code provides that any officer making an arrest for ⅝ narcotics violation shall seize and deliver to the State Division of Narcotic Enforcement any vehicle used to store, conceal, transport, sell or facilitate the possession of. narcotics, such vehicle “to be held as evidence until a forfeiture has been declared or a release ordered.” (Emphasis supplied.) Petitioner’s vehicle, which evidence showed had been used to carry oh his narcotics possession and transportation, was impounded by the officers and their duty required that it be kept “as evidence” until forfeiture proceedings were carried to a conclusion. The lower court concluded, as a matter of state law, that the state forfeiture statute did not by “clear and express language” authorize the officers to search petitioner’s car. 234 Cal. App. 2d, at 598, 44 Cal. Rptr., at 491. But the question here is not whether the search was authorized by state "law. The question is rather whether the search was reasonable under the Fourth Amendment. Just as a search authorized by state law may be an unreasonable one under that amendment, so may a search not expressly authorized by state law be justified as a constitutionally reasonable one. While it is true, as the lower court said, that “lawful custody of an automobile does not of itself dispense with constitutional requirements of searches thereafter made of it,” ibid., the reason for and nature of the custody may constitutionally justify the search. Preston was arrested for vagrancy. An arresting officer took his car to the station rather than just leaving it on the street. It was not suggested that this was done other than for Preston’s convenience or that the police had any right to impound the car and keep it from Preston or whomever he might send for it. The fact that the police had custody of Preston’s car was totally'unrelated to the vagrancy charge for which they arrested him. So was their subsequent search of the car.* This case is not Preston, nor is it controlled by it. Here the officers seized petitioner’s car because they were required, to do so by state law. They seized it because of the crime for which they arrested petitioner. They seized it to impound it' and they had to keep it until forfeiture proceedings were concluded. Their subsequent search of the car — whether the State had “legal title” to it or not— was closely related to the reason petitioner was arrested, the reason his car had been impounded, and the reason it was being retained. The forfeiture of petitioner’s car did not take place until over four months after it was lawfully seized. It would be unreasonable to hold that the police, having to retain the car in their custody for such a length of time, had no right, even for their own protection, to search it. It is rio answer to say that the police could have obtained a search warrant, for “[t]he relevant test is not whether it is reasonable to procure a search warrant, but whether the search was reasonable.” United States v. Rabinowitz, 339 U. S. 56, 66. Under the circumstances of this case, we cannot hold unreasonable under the Fourth Amendment the examination or search of a car validly held by officers for use as evidence in a forfeiture proceeding.
Our holding, of course, does not affect the State’s power to impose higher standards on searches and seizures than required by the Federal Constitution if it chooses to do so. And when such state standards alone have been violated, the State is free, without review by us, to apply its own state harmless-error rule to such errors of state law. There being no federal constitutional error her.e, there is no need for us to determine whether the lower court properly applied its state harmless-error rule.
Affirmed.
Cal. Health &'Safety Code §11610 provides:
"The interest of any registered owner of a vehicle used to unlawfully transport or facilitate the unlawful transportation of any narcotic, or in which any narcotic is unlawfully kept, deposited, or concealed or which is used to facilitate the unlawful keeping, depositing or concealment of any narcotic, or in which any narcotic is unlawfully possessed -by ah occupant thereof or which is used to facilitate the unlawful possession of any narcotic by an occupant thereof, shall be forfeited to the State.”
Petitioner also presents the contention here that he was unconstitutionally deprived of the right to confront a witness against him, because, the State did not produce the informant to testify against him. This contention we consider absolutely devoid of merit.