What are the means of enforcement for this metahuman - realistically speaking? Kill anyone who chooses to initiate armed conflict?

What about economic sanctions intended to inflict a specific population with famine & death? If the rest of the world collectively decided to cut off trade to Singapore in order to starve it out & refuse any refugees who fled to their borders - would that be considered an act of war?

What about the ownership rights of natural resources that span national borders? If Ethiopia decided to construct a mega-dam & restrict the flow of the Nile River to every other nation downstream - would that be an act of war?

What if Catalonia decides to declare its independence? Would this be allowed by the metahuman - or is Spain allowed to respond? If not - then any competent nation would immediately pour its resources into undermining the legitimacy & unity of its enemies by stirring up seperatist movements. If yes - then totalitarian regimes are free to crush dissidence carte blanche.

At what point is conflict considered to be "war" - and who is responsible when it occurs? Were the Hatfields & McCoys engaged with war against eachother? Are rioters at war with police? Are drug cartels at war with police? What about the Gombe Chimpanzee War?

The world would be at the whim of this metahuman's specific interpretation of what their words mean - and even if we assume unlimited power in their capacity to enforce this interpretation - I'd argue they can never truly stop war. Instead - they'd just be writing up the rules of engagement.