lack, of alternative courses of action that do not rise to the level of a use of force. Should passive (as distinct from active) cyber defences like firewalls be adequate to reliably and completely thwart a cyber armed attack, other measures, whether cyber or kinetic, at the level of a use of force are impermissible. Similarly, if active cyber operations not rising to the level of use of force suffice to deter or repel an armed attack (imminent or on-going), forceful cyber or kinetic alternatives will be barred by the necessity criterion.
