From this Fox story:
WASHINGTON — The White House on Thursday asserted President Bush's executive privilege in refusing to disclose documents subpoenaed by the Senate in the investigation of alleged political firings of eight federal prosecutors. The announcement set off angry Democratic congressional leaders, who labeled the decision "stonewalling" and "obfuscation." "Maybe everyone has acted honorably. But show me an administration that craves secrecy and I'll show you an administration that probably has something to hide," Sen. Chuck Schumer, D-N.Y., who has led the probe.
Charles E. Schumer, D-N.Y., who is leading the Senate probe into the firings, said, “It’s now up to the president. Is the White House going to cooperate with an investigation that has rocked the Justice Department, or will they continue to stonewall?”