White House officials notified a House committee of the rare assertion about 15 minutes before the committee was to vote on holding the head of the EPA and a White House budget official in contempt of Congress for not providing the documents.
The committee's chairman, Rep. Henry Waxman, D-Calif., then canceled the vote while expressing skepticism over the privilege claim.
"I have a clear sense that their assertion of this privilege is self-serving and not based on the appropriate law and rules," Waxman said from the dais of the House Oversight and Government Reform Committee hearing room.
"I don't think we've had a situation like this since Richard Nixon was president when the president of the United States may have been involved in acting contrary to law, and the evidence that would determine that question for Congress in exercising our oversight is being blocked by an assertion of executive privilege," he said.
Waxman said he wanted to review Attorney General Michael Mukasey's rationale for the executive privilege claim before deciding what to do next. He said he would not abandon his attempts to get what he wants from EPA Administrator Stephen Johnson and Susan Dudley, administrator for information and regulatory affairs at the White House Office of Management and Budget.
Executive privilege, while not explicitly mentioned in the Constitution, is grounded in the constitutional doctrine of separation of powers and is sometimes invoked to keep executive branch deliberations private.
Mr. Bush has also asserted executive privilege to keep his chief of staff, Josh Bolten, and former White House counsel Harriet Miers from having to provide information to Congress about the firing of a group of U.S. attorneys in what Democrats consider a political purge.
In February the Democratic-led House voted to hold Miers and Bolten in contempt of Congress despite the assertion of executive privilege. When Mukasey refused to refer the contempt citations to a federal grand jury, the House Judiciary Committee sued in federal court to enforce them, arguing that Bush was making an overly broad use of executive privilege.
Waxman contends the White House intervened with EPA to produce more industry-friendly outcomes in setting new smog standards and denying California and more than a dozen other states permission to cut greenhouse gas emissions from cars and trucks.
EPA and White House officials have turned over thousands of pages of documents in response to Waxman's subpoenas, but Waxman contends they are keeping back some that would clearly reveal President Bush's role.
These include documents about Mr. Bush's participation in the smog decision, talking points on the smog rule for Johnson to use with Mr. Bush, and communications about preparing talking points for Mr. Bush to use in discussing the greenhouse gas waiver with California Gov. Arnold Schwarzenegger.
These documents and others are referenced in a June 19 letter from Mukasey to Mr. Bush supporting a claim of executive privilege to block their release. The letter was provided Friday to Waxman's committee.
"I believe that publicly releasing these deliberative materials to the committee could inhibit the candor of future deliberations among the president's staff in the (Executive Office of the President) and deliberative communications between the EOP and executive branch agencies, particularly deliberations concerning politically charged issues," Mukasey wrote.
"Accordingly, I conclude that the subpoenaed materials at issue here fall squarely within the scope of executive privilege."
A congressional committee can overcome an executive privilege claim if the documents in question are critical to fulfilling its functions, Mukasey said, but he argued that's not the case here. He cited the many documents Waxman already has received and the conclusions he's been able to draw from them.
On the smog issue, EPA and White House officials have acknowledged that only hours before the rule was announced in March, Bush intervened directly on behalf of White House staff who opposed a tougher standard to protect the environment from smog.
On the California greenhouse gas issue, Waxman's committee staff produced a report last month concluding from interviews with high-level EPA officials that Johnson initially supported giving California full or partial permission to limit tailpipe emissions - but reversed himself after hearing from the White House. Waxman contends such intervention by the White House could be illegal since the outcome, according to Waxman, runs contrary to the Clean Air Act.
More than a dozen other states were also blocked from implementing the tailpipe emission limits after Johnson rejected California's request for a required federal waiver in December.