There are various opinions on the relevance of the United Nations concerning the authorisation of the use of force. Idealists demand UN authorisation for any type of intervention and strict adherence to a narrow interpretation of international law. Realists have a more sceptical stance, arguing that international law and international institutions are only successful under specific circumstances. Neoconservatives defy international law and international institutions. These arguments are compared and then applied to several case studies. It is explained why unilateralist thinking is not viable; why the use of force in circumvention of the UN framework is never legal; and that cases where intervention is illegal but legitimate necessitate reform of international laws and institutions.