Local decisions are taken by those who participate in the local environment. For example, the members of a family or a community are free to choose among themselves what lifestyle they will pursue, and what rules they will live by. They are not free to impose those rules on other families or communities, but they are completely free to make those choices that apply to just themselves.
Coordinating bodies are established as necessary to coordinate the interactions between different groups, and to resolve any conflicts that develop among them. Smaller groups will choose representatives that will speak for them within the coordinating bodies of bigger groups. From those coordinating bodies representatives will again be chosen that will represent this bigger group in a coordinating body of an even bigger group. And so forth.
Power originates at the smallest local level and is delegated into bigger and bigger groups for the purpose of coordination. At no point is the local power given up. The bigger groups only exist for the purpose of coordination among the smaller groups, and for representing the smaller groups in a bigger forum. The representatives of the bigger groups will never meddle in the internal affairs of the smaller groups, but will only mediate in conflicts among those groups when necessary. The purpose of representatives is to represent groups externally, never to impose rules on the internal affairs of groups.
You can see it as circles grouping together into bigger circles, that again group into even bigger circles, and so on.
If A is a small local group, it might benefit from cooperating with other groups of size A and form a bigger group, that we could call B. Each of the A groups will send representatives to some kind of coordinating body for group B. Those representatives will together sort out any conflicts that might develop between the A groups. Group B has no business dealing with the internal affairs of any of the A groups, unless invited to do so. Group B can however decide rules for the interaction between the A groups, as necessary. Group B can also elect representatives that will represent all of Group B, which includes all the A groups, externally. That is, in bigger forums, in relating to other groups of groups.
Several class B groups can band together to form a Group C. It would again have a coordinating body consisting of representatives from several B groups. Its business would be to create optimum interactions between different B groups, to encourage cooperation, and to mediate conflicts between B groups when necessary. The coordinating body of Group C would have no concern at all about A groups, but would only deal with the intercourse between B groups. The Group C representatives would also be concerned with the world outside the C group, being the caretakers of the cumulative interests of Group C, and working on optimizing Group C's role within an even bigger playing field.
This can go all the way up to a coordinating council for the whole planet. The scope of planetary council members' business would be the optimum interaction between the major geographical and cultural regions on the planet. It would also be their business to represent the whole planet in any interactions with representatives of other planets.
Notice that integral to this scheme is the principle that power flows from the ground up. Power flows from individuals to communities to societies to civilizations. It doesn't go the other way. It is not the business of governments to grant rights or privileges to individuals or communities. The people grant limited privileges to their representatives, bestowing them the job of representing them well. The privileges of representatives can be revoked at any time by those bestowing that power.
Global or regional leaders will not command armies. They will not control economies. They will not control energy resources. There are no reins of power that can be usurped by somebody mistakenly elected to a high office.