Be very specific perhaps just choosing one area such as Humanitarian Intervention, where an organization should be established that would intervene automatically to stop the sort of slaughter we have witnessed in places like Sudan, Rwanda, Syria and also pose challenges to unilateral interventions like Iraq.
Or you could focus on health. Or the environment. OR you could imagine the world in 2075 and describe in a sort of fictional way how the world came to believe that such government and law had to replace the current system. Be creative. You can throw in world wars, apocalypses, asteroids, alien invasions to boost the incentive for a reorganization of international relations.