They must have signed a contract saying that they could not release the originals of their work without bush's permission because this is what congress would need to look at to determine how Bush falsified scientific research in his favor.
As the Wonk Room’s Brad Johnson reports, President Bush today exerted executive privilege to block the House Oversight Committee’s subpoenas for EPA documents on global warming, heading off a scheduled contempt vote for EPA Administrator Stephen Johnson and White House Office of Management and Budget regulatory administrator Susan Dudley. Committee chairman Henry Waxman’s (D-CA) blistering response to the news:
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. I would hope and expect this administration would not be making this assertion without a valid basis for it, but to date I have not seen a valid instance of their executive privilege.