with whom Mr. Justice Brennan joins, concurring in part and concurring in the judgment.
I agree with Mr. Justice Stevens that the Government’s warrantless projection of the films constituted a search that infringed petitioners’ Fourth Amendment interests despite the fact that the Government had acquired the films from a private party.1 I write separately, however, because I disagree with Mr. Justice Stevens’ suggestion that it is an open question whether the Government’s projection of the films would have infringed any Fourth Amendment interest if private parties had projected the films before turning them over to the Government, ante, at 657, n. 9. The notion that private searches insulate from Fourth Amendment scrutiny subsequent governmental searches of the same or lesser scope is inconsistent with traditional Fourth Amendment principles. Nor does it follow from our recognition in Burdeau v. McDowell, 256 U. S. 465 (1921), and Coolidge v. New Hampshire, 403 U. S. 443, 487-490 (1971), that the Fourth Amendment proscribes only governmental action.2
*661I agree with Me. Justice Stevens that there was “nothing wrongful” about the Government’s examination of the contents of the packages that had been opened by private parties. When the private parties turned the films over to the Government, the packages already had been opened, and the Government saw no more than what was exposed to plain view. No, Fourth Amendment interest was implicated by this conduct because the opening of the packages cannot be attributed to the Government and considered a governmental search.3 As the Court noted in Coolidge v. New Hampshire, supra, at 489, where a private party produced evidence for government inspection, “it was not incumbent on the police to stop her or avert their eyes.”
This does not mean, however, that the Government subsequently may conduct the same kind of search that private parties have conducted without implicating Fourth Amendment interests. The contrary view would permit Government agents to conduct warrantless searches of personal property whenever probable cause exists as a result of a prior private search. We have previously held, however, that police must obtain a warrant before searching a suspect’s luggage even *662if they have probable cause to believe that it contains contraband. Arkansas v. Sanders, 442 U. S. 753 (1979); United States v. Chadwick, 433 U. S. 1 (1977). The fact that such probable cause may be the product of a private search would not alter the need to comply with the warrant requirement. Thus, if the private parties in these cases had projected the films before turning them over to the Government, the Government still would have been required to obtain a warrant for its subsequent screening of them. As Mr. Justice Stevens recognizes, petitioners possessed a legitimate expectation of privacy in the films, and this expectation was infringed by the Government’s unauthorized screening of them. Unlike the opening of the packages that destroyed their privacy by exposing their contents to the plain view of subsequent observers, a private screening of the films would not have destroyed petitioners’ privacy interest in them. Thus the Government’s subsequent screening of the films constituted an independent, governmental search that would have infringed petitioners’ Fourth Amendment interests without regard to any previous screening by private parties.
I therefore concur in part and in the judgment.
Although Mr. Justice SteveNs’ opinion refers to the films as having been “lawfully acquired” by the Government, ante, at 651, 654, 656, I note that he does not reach the question whether the Government’s acquisition of the films was a “seizure” subject to the warrant requirement of the Fourth Amendment, ante, at 653, n. 4, a question on which the Court of Appeals was divided. 592 F. 2d 788, 792-793, 800-802 (CA5 1979). Likewise, I do not address this question.
Neither Burdeau v. McDowell nor Coolidge v. New Hampshire supports the proposition that private searches insulate subsequent governmental searches from Fourth Amendment scrutiny. In Burdeau the Court held that the actions of a private party in illegally seizing evidence will not be attributed to the Government 'for Fourth Amendment purposes *661when the private party turns the evidence over to the Government. The Court noted that because “no official of the Federal Government had anything to do with the wrongful seizure of the petitioner’s property, . . . [i]t is manifest that there was no invasion of the security afforded by the Fourth Amendment against unreasonable search and seizure, as whatever wrong was done was the act of individuals in taking the property of another.” 256 U. S., at 475. Similarly, in Coolidge v. New Hampshire, the Court held that a wife’s voluntary action in turning over to police her husband’s guns and clothing did not constitute a search and seizure by the government-. 403 U. S., at 487-490.
Because the private party’s opening of the packages exposed their contents to plain view and made it unnecessary for the FBI agents to open the packages, there was no governmental search when the FBI viewed their contents. Except in such circumstances, I do not understand how a third party’s inspection of a package’s contents “could be so complete that there would be no additional search by the FBI when it re-examines the materials,” ante, at 659, n. 14.