Well - good questions all - and unfortunately there is no right or universal God given answer. And I certainly do not pretend to have one.
In the meantime this court spent $8B of money without demonstrable outcomes beyond embarrassing itself. Thus it is mere window dressing presenting a false picture about effective international law. 

Perhaps it is time to admit that international law is rather ethereal - not reaching much beyond specific ( trade ) contract enforcement. And our future will be built better if we were to actually focus on the future, what it should be - and not drive into it looking at our rear view mirrors. 

Lastly given our extensive multiplicity of cultures, legal systems, power politics ...  it is naive to expect short term solutions. A more strategic aproach is called for - probably generational time frames.