I think this is where you'd have to have presumptions about the carbon content in the import that would have to be based on rough figures from wherever the origin of the product is, and what kind of energy sources they're using, and presumptions about the energy sources that are built into the products. I think the only way it could be done in any practicable way is with rough-and-ready calculations or rough-and-ready judgments. That's why there's a potential problem with protectionist implications of a tax based on that approach.
And you'd have to make sure it satisfies WTO standards. That trade stuff is something I haven't done. I know there's a precedent for it out there, using presumptions about what the...probably, I admit, in a more simple context than carbon. Carbon enters into everything, and that makes it a problem.