Sure. You said that the ICC claimed jurisdiction over all territory worldwide though. And part of the inherent nature of authority is the ability to delegate

Sure. You said that the ICC claimed jurisdiction over all territory worldwide though. And part of the inherent nature of authority is the ability to delegate that authority; it's absurd for the USA to accept that Vietnam has jurisdiction over crimes committed in Vietnam but threaten to go to war if Vietnam asks the ICC to hear a charge rather than having it heard in Vietnamese courts.