The philosophy of social contact dictates that governments responsibility is to protect it's people and the responsibility of the people is to allow their government to protect them.
Thus the responsibility of the government of the Global Powers is to establish a defense force in order to eliminate threats that would harm the good of the region (as could have been used in the Diol conflict in which the use of nuclear arms was deemed as a viable option) the citizens of the global powers have e obligation to offer the government their support.
Thus a certain percentage of a nation's military force must be obligated to the creation of a global powers defense force (we are taking like a fraction of a percent) and as a replacement or increase in regional standing nuclear weapons can be turned over to regional authority.
If you comply then you are recognized as a citizen as may vote in election proposals amendments etc. If you give more then you are rewarded with a greater degree of vote
(like citizen gets on vote and nuclear citizens get two votes)