...authority to respond to a Ukrainian request for assistance, including armed force. So, while the collective
self-
defense obligation of Article 5 of the NATO treaty does not embrace non-NATO Ukraine, the inherent right of collective
self-
defense under international law and the UN Charter applies. The allied governments of NATO should unequivocally signal that they do not shy away from inherent collective
self-
defense of Ukraine or any other nation invaded by an aggressor state. Otherwise, Putin may miscalculate that the absence of a treaty obligation for
self-
defense deprives the United States...