Thank you Paul...

I read that as "there ought to be a law..." not IS one.

There is an agreement but the only time it's ever been used is Canada/Russia where Canada claimed a well documented $14 million radiation spill cleanup,
Russia only paid $3,000,000. There doesn't appear to be an appeal court to protest to...

Which means the UN would have to forge an agreement as law and than enforce it.
With the 3 biggest polluters holding veto power, I expect no further progress.

Yet another example where the current world politics is 80% show and 20% actually DO.