You don't need to use international law to create an international crime. For example, many countries have laws against the sexual exploitation of children tha

You don't need to use international law to create an international crime. For example, many countries have laws against the sexual exploitation of children that apply internationally. If the French government, say, wants to punish French executives who damage the environment anywhere in the world they can do this. The situation is a little more complicated with the EU (they make rules which get implemented in national law) but the effect is much the same.