Senate Judiciary Committee Chairman Patrick Leahy, D-Vt., complained to Mukasey that after five years of efforts to glean the information, the committee still has seen only a fraction of the documents it is seeking.

"There is no legitimate argument for withholding the requested materials from this committee," Leahy wrote in a letter to Mukasey that accompanied the subpoena.

The Justice Department blasted the subpoena as a partisan move.

"We have worked in good faith over the past several months to see that the Judiciary Committee's legitimate oversight requests were being met in a manner consistent with the Justice Department's equally legitimate and long-standing need to provide confidential legal advice within the executive branch," department spokesman Brian Roehrkasse said. "We will now assess our next steps."