Ah, these guys make it more clear than I do:
1) California recently passed a law requiring automakers to make vehicles that emit less global warming gases.
2) The automakers are threatening to sue (possibly as soon as January) instead of making the cleaner cars.
3) This law sets an extremely important national precedent because California is the only state permitted to set its own tailpipe standards, but other states may adopt California standards.
4) Consumers should write to the automakers urging them to use their engineers, not their lawyers, to help solve global warming.
The action alert is on our website here