The state of California has filed a lawsuit challenging the Environmental Protection Agency’s decision to block it from enacting tough tailpipe-emission requirements for cars, SUVs and light trucks.

In announcing the lawsuit, filed on Jan. 2, California Gov. Arnold Schwarzenegger (R) said, “It is unconscionable that the federal government is keeping California and nineteen other states from adopting these standards.”

EPA had denied California’s request for a waiver on Dec. 19, citing concerns about having multiple state pollution standards.

California’s program would require automobile manufacturers to reduce greenhouse-gas emissions from new cars and light trucks, beginning in 2009. The new federal energy measure, enacted Dec. 19, imposes a 35-mile-per gallon fuel-economy standard for vehicles by 2020 but does not address carbon dioxide emissions.

In its suit, filed in the 9th U.S. Circuit Court of Appeals in San Francisco, California was joined by environmental groups such as the Sierra Club and 15 other states that have developed similar vehi-cle-emission plans. But at EPA, spokesman Jonathan Shradar says, “We’re moving forward and looking to the beneficial national approach in the energy bill, as opposed to a patchwork of state policies.”

David Bookbinder, the Sierra Club’s chief climate counsel, thinks California and its allies will prevail in the lawsuit. “We are confident that this court will join the others that have ruled in our favor on global warming issues, although we regret having to go to court in order to force the Bush administration to obey the law.”

Some in Congress lambasted EPA’s decision. Senate Environment and Public Works Committee Chairman Barbara Boxer (D-Calif.) demanded that EPA Administrator Stephen Johnson turn over all documents relating to the agency’s decision. She scheduled a Jan. 10 hearing on the issue and says the committee “will hold the Bush EPA accountable for this outrageous, unprecedented decision.”

Although EPA initially said it would comply with the committee request, it missed the Jan. 7 deadline. In a Jan. 4 letter to Boxer, Johnson noted, “Your request is a top priority for the agency.”