The purpose of this proposed tax is clear. French industries are having a tough time trying to meet Kyoto's required goals, and doing so is costing them a pretty penny. This drives up the cost of their goods for export, which makes them less competitive than their American counterparts.
The French aren't all that bright as a country. They have a tendency to refuse to admit that they made a mistake with Kyoto, and to compound the error, they want to patch their economy with a tariff against their primary competition. However, the solution is simple - repeal Kyoto and immediately French goods will become more marketable and competitive.
But the French aren't likely to ever admit that George W. Bush was right, or that the Americans in this case had a lot more common sense.
(The Kyoto treaty was designed specifically to diminish the United States. When the U.S. pulled out after GWB was inaugurated, the treaty became an embarrassment and punishing mistake for those who remained in the treaty. Just ask Canada if one doubts.)
IIRC, the Kyoto thing was rejected by something like 95 to 5 in the senate during B.J.'s last term.