Unless taken in self-defense (and even then for only a limited period of time), the UN Charter forbids all use of force taken without the approval of the Security Council. But the meaning of this self-defense exception is disputed.  Most countries read self-defence as lawful only in response to an attack.  But some countries argue it can be lawful against imminent attacks.  And very few – notably the U.S. – argue it may be used even against anticipated attacks.  The consequence is that some of Tillerson’s “military options” against the DPRK would be accepted as lawful by the international