The application of military force is often a matter of controversy. What one individual deems a just exertion of force, another labels as unwarranted violence. While self-defence is widely recognized as one justification for resorting to violence (as alluded to in the quote by George W. Bush) in many conflicts - from international wars to public house brawls - all those involved invoke this as a justification for their action. While doctrines such as the 'Just War' propose criteria for judging whether force is justified, whether the criteria have been met or whether they are even relevant in particular circumstances are readily contested. In terms of what kind of force can be used, varied national and international laws require organizations with official authority - such as the police and the military - to exert force proportional to the threat faced. What such general prescriptions mean for particular cases though, must be worked out in each case.