This still falls into the "country X doesn't do anything" trap. If France imposes a carbon duty but Britain doesn't, British companies will have access to chea

This still falls into the "country X doesn't do anything" trap. If France imposes a carbon duty but Britain doesn't, British companies will have access to cheaper goods. British citizens will have greater purchasing power and British companies will have an economic advantage. France might say, "Britain doesn't do anything about climate change" as they're supporting the carbon emissions in other countries by importing their goods. This would still only work if enough countries banded together to enforce it that it became too difficult to grow an international company without access to carbon duty countries.