dissenting.
Believing that the search by the police of the offices of the *571Stanford Daily infringed the First and Fourteenth Amendments’ guarantee of a free press, I respectfully dissent.1
I
It seems to me self-evident that police searches of newspaper offices burden the freedom of the press. The most immediate and obvious First Amendment injury caused by such a visitation by the police is physical disruption of the operation of the newspaper. Policemen occupying a newsroom and searching it thoroughly for what may be an extended period of time2 will inevitably interrupt its normal operations, and thus impair or even temporarily prevent the processes of newsgathering, writing, editing, and publishing. By contrast, a subpoena would afford the newspaper itself an opportunity to locate whatever material might be requested and produce it.
But there is another and more serious burden on a free press imposed by an unannounced police search of a newspaper office: the possibility of disclosure of information received from confidential sources, or of the identity of the sources- themselves. Protection of those sources is necessary to ensure that *572the press can fulfill its constitutionally designated function of informing the public,3 because important information can often be obtained only by an assurance that the source will not be revealed. Branzburg v. Hayes, 408 U. S. 665, 725-736 (dissenting opinion) ,4 And the Court has recognized that “ 'without some protection for seeking out the news, freedom of the press could be eviscerated.' ” Pell v. Procunier, 417 U. S. 817, 833.
Today the Court does not question the existence of this constitutional protection, but says only that it is not “convinced . . . that confidential sources will disappear and that the press will suppress news because of fears of warranted searches.” Ante, at 566. This facile conclusion seems to me to ignore common experience. It requires no blind leap of faith to understand that a person who gives information to a journalist only on condition that his identity will not be revealed will be less likely to give that information if he knows that, despite the journalist's assurance, his identity may in fact be disclosed. And it cannot be denied that confidential information may be exposed to the eyes of police officers who execute a search warrant by rummaging through the files, cabinets, desks, and wastebaskets of a newsroom.5 Since the indisputable effect of such searches will thus be to prevent a newsman from being able to promise confidentiality to his potential sources, it seems obvious to me that a journalist’s *573access to information, and thus the public’s, will thereby be impaired.6
A search warrant allows police officers to ransack the files of a newspaper, reading each and every document until they have found the one named in the warrant,7 while a subpoena would permit the newspaper itself to produce only the specific documents requested. A search, unlike a subpoena, will therefore lead to the needless exposure of confidential information completely unrelated to the purpose of the investigation. The knowledge that police officers can make an unannounced raid on a newsroom is thus bound to have a deterrent effect on the availability of confidential news sources. The end result, wholly inimical to the First Amendment, will be a diminishing flow of potentially important information to the public.
One need not rely on mere intuition to reach this conclusion. The record in this case includes affidavits not only from members of the staff of the Stanford Daily but also from many professional journalists and editors, attesting to precisely such personal experience.8 Despite the Court’s rejection of this *574uncontroverted evidence, I believe it clearly establishes that unannounced police searches of newspaper offices will significantly burden the constitutionally protected function of the press to gather news and report it to the public.
I — I H-1
In Branzburg v. Hayes, supra, the more limited disclosure of a journalist’s sources caused by compelling him to testify was held to be justified by the necessity of “pursuing and prosecuting those crimes reported to the press by informants and . . . thus deterring the commission of such crimes in the future.” 408 U. S., at 696. The Court found that these important societal interests would be frustrated if a reporter were able to claim an absolute privilege for his confidential sources. In the present case, however, the respondents do not claim that any of the evidence sought was privileged from disclosure; they claim only that a subpoena would have served equally well to produce that evidence. Thus, we are not concerned with the principle, central to Branzburg, that “ 'the public . . . has a right to every man’s evidence,’ ” id., at 688, but only with whether any significant societal interest would be impaired if the police were generally required to obtain evidence from the press by means of a subpoena rather than a search.
It is well to recall the actual circumstances of this litigation. The application for a warrant showed only that there was reason to believe that photographic evidence of assaults on the police would be found in the offices of the Stanford Daily. There was no emergency need to protect life or property by an *575immediate search. The evidence sought was not contraband, but material obtained by the Daily in the normal exercise of its journalistic function. Neither the Daily nor any member of its staff was suspected of criminal activity. And there was no showing that the Daily would not respond to a subpoena commanding production of the photographs, or that for any other reason a subpoena could not be obtained. Surely, then, a subpoena duces tecum would have been just as effective as a police raid in obtaining the production of the material sought by the Santa Clara County District Attorney.
The District Court and the Court of Appeals clearly recognized that if the affidavits submitted with a search warrant application should demonstrate probable cause to believe that a subpoena would be impractical, the magistrate must have the authority to issue a warrant. In such a case, by definition, a subpoena would not be adequate to protect the relevant societal interest. But they held, and I agree, that a warrant should issue only after the magistrate has performed the careful “balancing] of these vital constitutional and societal interests.” Branzburg v. Hayes, supra, at 710 (Powell, J., concurring) .9
The decisions of this Court establish that a prior adversary judicial hearing is generally required to assess in advance any threatened invasion of First Amendment liberty.10 A search by police officers affords no timely opportunity for such a *576hearing, since a search warrant is ordinarily issued ex parte upon the affidavit of a policeman or prosecutor. There is no opportunity to challenge the necessity for the search until after it has occurred and the constitutional protection of the newspaper has been irretrievably invaded.
On the other hand, a subpoena would allow a newspaper, through a motion to quash, an opportunity for an adversary hearing with respect to the production of any material which a prosecutor might think is in its possession. This very principle was emphasized in the Branzburg case:
“[I]f the newsman is called upon to give information bearing only a remote and tenuous relationship to the subject of the investigation, or if he has some other reason to believe that his testimony implicates confidential source relationships without a legitimate need of law enforcement, he will have access to the court on a motion to quash and an appropriate protective order may be entered.” 408 U. S., at 710 (Powell, J., concurring).
See also id., at 707-708 (opinion of Court). If, in the present litigation, the Stanford Daily had been served with a subpoena, it would have had an opportunity to demonstrate to the court what the police ultimately found to be true — that the evidence sought did not exist. The legitimate needs of government thus would have been served without infringing the freedom of the press.
Ill
Perhaps as a matter of abstract policy a newspaper office should receive no more protection from unannounced police searches than, say, the office of a doctor or the office of a bank. But we are here to uphold a Constitution. And our Constitution does not explicitly protect the practice of medicine or the business of banking from all abridgment by government. It does explicitly protect the freedom of the press.
*577For these reasons I would affirm the judgment of the Court of Appeals.
1 agree with the Court that the Fourth Amendment does not forbid the issuance of search warrants “simply because the owner or possessor of the place to be searched is not then reasonably suspected of criminal involvement.” Ante, at 560. Thus, contrary to the understanding expressed in the concurring opinion, I do not “read” anything “into the Fourth Amendment.” Ante, at 568. Instead, I would simply enforce the provisions of the First Amendment.
One search of a radio station in Los Angeles lasted over eight hours. Note, Search and Seizure of the Media: A Statutory, Fourth Amendment and First Amendment Analysis, 28 Stan. L. Rev. 957, 957-959 (1976).
See Mills v. Alabama, 384 U. S. 214, 219; New York Times Co. v. Sullivan, 376 U. S. 254, 269; Grosjean v. American Press Co., 297 U. S. 233, 250.
Recognizing the importance of this confidential relationship, at least 26 States have enacted so-called “shield laws” protecting reporters. Note, The Newsman’s Privilege After Branzburg: The Case for a Federal Shield Law, 24 UCLA L. Rev. 160, 167 n. 41 (1976).
In this ease, the policemen executing the search warrant were con-cededly in a position to read confidential material unrelated to the object of their search; whether they in fact did so is disputed.
This prospect of losing access to confidential sources may cause reporters to engage in “self-censorship,” in order to avoid publicizing the fact that they may have confidential information. See New York Times Co. v. Sullivan, supra, at 279; Smith v. California, 361 U. S. 147, 154. Or journalists may destroy notes and photographs rather than save them for reference and use in future stories. Either of these indirect effects of police searches would further lessen the flow of news to the public.
The Court says that “if the requirements of specificity and reasonableness are properly applied, policed, and observed” there will be no opportunity for the police to “rummage at large in newspaper files.” Ante, at 566. But in order to find a particular document, no matter how specifically it is identified in the warrant, the police will have to search every place where it might be — including, presumably, every file in the office — and to examine each document they find to see if it is the correct one. I thus fail to see how the Fourth Amendment would provide an effective limit to these searches.
According to these uneontradicted affidavits, when it becomes known that a newsman cannot guarantee confidentiality, potential sources of infor*574mation often become unavailable. Moreover, efforts are sometimes made, occasionally by force, to prevent reporters and photographers from covering newsworthy events, because of fear that the police will seize the newsman’s notes or photographs as evidence. The affidavits of the members of the staff of the Stanford Daily give examples of how this very search produced such an impact on the Daily’s own journalistic functions.
The petitioners have argued here that in fact there was reason to believe that the Daily would not honor a subpoena. Regardless of the probative value of this information, it is irrelevant, since it was not before the magistrate when he issued the warrant. Whiteley v. Warden, 401 U. S. 560, 565 n. 8; Spinelli v. United States, 393 U. S. 410, 413 n. 3; Aguilar v. Texas, 378 U. S. 108, 109 n. 1; see Johnson v. United States, 333 U. S. 10, 13-14.
E. g., United States v. Thirty-seven Photographs, 402 U. S. 363; Carroll v. Princess Anne, 393 U. S. 175; Freedman v. Maryland, 380 U. S. 51. Cf. Roaden v. Kentucky, 413 U. S. 496; A Quantity of Books v. Kansas, 378 U. S. 205; Marcus v. Search Warrant, 367 U. S. 717.