If adapted by the whole world it would be such a wonderful thing both for environment and economies because it would incentivize development and adoption of new clean tech. Because otherwise people would simply “outsource” the pollution which is, of course, a ridiculous concept.
The duty can be a flat rate or an average emissions per economic output for the country.
For instance, it does not say that in TFA, but it is implied that some sort of fund would have to be created to manage and distribute all that new money. Let's consider that, as a natural consequence, a big part of that money goes to buying carbon credits/offsets; that's a billion euro bill that is going to make "the right person" very rich, very fast.
And before one says something like "but we are not like that", just remember Austria just came out of a huge political crisis a few years ago. Imagine what would happen to this money in other least developed countries.
A possible solution would be to keep things as democratic and transparent as they could possibly be.