If the world's culture is strongly set against having armies, and one country effectively threatens them by breaking that taboo, then I would at least expect the world to instantly cease all trade and transport links with the arming country.

That may not be enough on its own to force the taboo-breaking country to disarm, but I don't see any contradiction in a world culture which is against having armies while also ruthlessly dedicated to temporarily re-arming and exterminating the first country that breaks the taboo.

There are hard coordination and rule of law / presumption of innocence questions to solve there, but I don't think we can necessarily assume that this world culture will stand idly by while their enemy works to undo the very thing that defines the culture.