Petitioner brought a District Court suit against various state prison officials alleging that, in violation of his constitutional rights, they used excessive force when transferring him from one cell to another. Although he waived a jury trial and initially consented to have a magistrate try the entire case pursuant to 28 U.S.C. 636(c)(1), petitioner was permitted at trial to withdraw his consent to the Magistrates jurisdiction. However, the Magistrate ruled that he was nonetheless authorized to conduct an evidentiary hearing and to submit proposed findings of fact and a recommended disposition to the court under 636(b)(1)(B), which authorizes the nonconsensual referral to magistrates for such purposes "of applications for post-trial relief made by individuals convicted of criminal offenses and of prisoner petitions challenging conditions of confinement." (Emphasis added.) The District Court overruled petitioners objection to the Magistrates role and accepted the Magistrates recommended findings and judgment for defendants. The Court of Appeals affirmed