> For the sake of brevity, read "countries" as "ministries of energy in countries" or "relevant public or privatized equivalents of ministries of energy in countries" - there's many modes of governance when it comes to this. A good example of "illegal for countries" in this sense would be if the EU made their member countries adopt jurisprudence in this matter through implementation via their own respective national laws.

What do you do if some countries don't want to play ball, and they turn out to be the biggest emitters?