Defense lawyers claimed the recording was an egregious violation of attorney-client privilege and asked for a dismissal. They alleged that agents with the Bureau of Alcohol, Tobacco, Firearms and Explosives had reviewed recordings of about 40 telephone calls and provided written reports on them to the U.S. Attorney's Office.
Prosecutors denied the allegations and said they received only a listing of the calls made.
Kimball ruled the government had a legitimate reason for subpoening the telephone records from the jail - investigators say they had reason to believe Zajac had made incriminating statements to the press and family members - and noted that the ATF and the U.S. Attorney's Office stated they did not review recordings that could be protected by attorney-client privilege.
The judge also denied a motion to throw out two charges that Zajac used explosives to damage a building used in any activity affecting interstate commerce. Zajac's attorneys contended that library operations do not affect out-of-state businesses.
But Kimball said businesses in the library, including a florist and a comic book shop, affect commercial activity. In addition, the building is home to national public radio station KCPW and a repository and lender of books purchased out of state, he said.
Zajac, 54, an Illinois man who formerly lived in Salt Lake City and Provo, is charged with six felonies.
Investigators think he carried a small pipe bomb concealed in a paper bag into the library Sept. 15, 2006. The device exploded on the third floor of the building, destroying a large double-paned window but causing no injuries.
