A powerful congressman will not be forced to testify in the perjury trial of baseball legend Roger Clemens, a judge ruled Monday, siding with federal prosecutors and lawyers for the House of Representatives.

Clemens’s defense team had subpoenaed Rep. Darrell Issa (R-Calif.), chairman of the House Committee on Government Oversight and Reform, to take the witness stand about 2008 hearings in which the former pitcher testified; Clemens is accused of lying during those hearings and to congressional investigators when he denied having ever used performance-enhancing drugs.

Court papers from both sides foreshadowed a titanic constitutional clash during arguments Monday, but U.S. District Judge Reggie Walton decided the matter on narrower grounds. He ruled that Issa would probably not have been able to provide “competent” testimony about the decision-making process used by legislators to hold the hearing. Issa was not even the ranking Republican on the committee in 2008.

The judge also said he was concerned that allowing defense lawyers to call Issa would lead to a “swearing match” as lawmakers offered their impressions of the relevance of Clemens’s testimony and the legitimacy of the proceedings.

Prosecutors must prove that Clemens’s alleged lies were “material,” or relevant to Congress’s work, and that the hearing served a legitimate legislative purpose.

The defense team has called the hearing a “show trial” designed to garner publicity, and Issa had been extremely critical of the proceeding, essentially calling it a witch hunt. Clemens’s attorneys hoped that Issa would echo those comments on the witness stand.

House lawyers sought to block Issa’s testimony, arguing that the lawmaker was too busy and was protected by a relatively obscure provision of the Constitution known as the “speech or debate” clause that is designed to shield lawmakers from interference with their official duties by other branches of government. Clemens’s lawyers countered that their client’s right to a fair trial and to confront his accusers trumped such protections.

Though Walton did not rule on the constitutional questions, he said he would likely have ruled that Issa was protected by the “speech or debate” clause.

Legal experts said last week that they expected Walton to rule in favor of House lawyers, though they noted that the showdown highlighted a central absurdity of the trial: Lawmakers, the alleged victims who requested the Justice Department investigation, have elected not to testify at Clemens’s trial on charges of perjury, obstruction of Congress and making false statements. Instead, the committee tapped a top staffer to tell jurors that the hearings were a proper use of congressional power.

Issa has aggressively used his own subpoena power to investigate the Justice Department and complained that the attorney general has not fully complied with his demands.