States' rights (unless they're wrong)
The US EPA has rejected California's request for a waiver to enforce a law set to take effect in 2009 that would require substantial cuts in greenhouse gas emission from cars and trucks sold in the state. This decision leaves the law in limbo for now - 15 other states have or are expected to adopt the same regulations.
Two federal courts have ruled that the the states are within their right to enforce such a law, provided the EPA granted the waiver, and the US Supreme Court has ruled that carbon dioxide, the main greenhouse gas targeted by the law, is a type of pollution that must be regulated under the Clean Air Act.
Rest assured, Gov. Arnold Schwarzenegger and Attorney General Jerry Brown will look for a chance to sue.
It will be interesting to see how the presidential hopefuls react to the news, especially the Republicans, who have used the states' rights argument when explaining their opposition to abortion (as in, the individual states should decide whether abortion is legal).