Ps, seven prisoners in the custody of the Department of Corrections of the State of California, filed a class action alleging substantial constitutional violations in the manner in which the California Adult Authority carries out its function of determining the length and conditions of punishment for convicted criminal offenders. Ps submitted requests for the production of documents pursuant to Rule 34. The 'Adult Authority files,' requested are composed of the personnel files of all members and employees of the Adult Authority, all Adult Authority documents relating to its past, present, or future operation, and all memoranda written by the Chairman of the Adult Authority within the preceding five years. The 'prisoners' files' was a request to examine the files of every twentieth inmate at each California Department of Corrections institution. Ds objected, claiming that the files were irrelevant, confidential, and privileged, and suggesting that they should not be required to turn over the files to Ps without prior in camera review by the District Court to evaluate the claims of privilege. P moved, under Rule 37, for an order compelling discovery. The Magistrate recommended that the District Court order production of the Adult Authority files without undertaking an in camera inspection of the files. This recommendation was accepted and the court ordered the production of the documents. The court also issued a protective order limiting the number of people associated with Ps who could examine those documents; only counsel of record and no more than a total of two investigators designated by such counsel, and then only to the extent necessary to the conduct of this action could examine the documents. Ds filed a petition for a writ of mandamus under 28 U.S.C. § 1651(a), requesting the Court of Appeals vacate the order granting Ps' motion to compel discovery. The Court of Appeals denied the petition. It concluded first that since 'the question of relevancy 'is to be more loosely construed at the discovery stage than at the trial,' issuance of the writ on the grounds of the asserted irrelevance of the documents in question was inappropriate. It held that the documents were part of 'a proper line of attack' in the underlying lawsuit. The Supreme Court granted certiorari.