Treasury Department officials told a federal court today that the Competitive Enterprise Institute is not entitled to receive copies of more than 7,300 internal emails concerning carbon taxes that the government had previously conceded exist and granted the think tank's request for a waiver of reproduction costs.

In a response filed with the U.S. District Court for the District of Columbia, which is hearing CEI's appeal of Treasury's refusal to produce the emails without pre-payment of the fees, the Treasury Department said the conservative non-profit "is not entitled to the relief requested, or to any other relief whatsoever, and requests that this action be dismissed in its entirely with prejudice and that Defendant be given such other relief as this Court deems proper, including costs and disbursements."

The Treasury Department filing was the latest development in a case that began last November when CEI appealed to the federal court to reverse Treasury's decision not to produce the emails after the think tank requested them in a Freedom of Information Act request.

Christopher Horner, a CEI senior fellow, told The Washington Examiner that he believes Treasury decided to demand the payment after receiving "not a little bit of heat for having admitted to 7,300 emails just in one sleepy office with nothing to do but wait for energy tax revenues, apparently to blow on the $100 billion per year fund the president promised to the world in Copenhagen!"

Environmentalists have long sought to tax use of fossil fuels that produce carbon emissions because they believe are linked to global warming. But no president has ever proposed a carbon tax, and none has been approved by Congress. President Obama told a 2010 global warming conference in Copenhagen that he supports a carbon tax.

The emails sought by CEI represented discussions among Treausury officials and possibly include conversations with the Obama White House as well.

A Treasury Department spokesman declined to comment.

Horner noted that today's filing appears to contradict assurances given by the Treasury Department recently to Sen. David Vitter, R-LA, that the "Treasury Department has granted a fee waiver to CEI and is committed to fulfilling its obligations under FOIA..."

Vitter is the ranking minority member of the Senate Environment and Public Works Committee.