Comparative Review of Iran and US Interance to Syria Crisis from perspective of International Law

The rise of Arab Nations against their rulers or Arab Spring was a start point of important political changes. One of those countries was Syria that its developments changed international environment. This paper studies the Syria crisis and US – Iran’s reasons for entrance in this crisis. What is juridical reasoning of two countries? Finding a legal response for this critical question can a basic for other activities after Syria crisis. According to conclusions of this paper, entrance of Iran to Syria crisis was following of demand of Damascus and this entrance can be a legitimate Defense not an offence. However, the US entrance to Syria crisis don’t have a legal and legitimate base. Reference of US to new theories and doctrines is insufficient justify its intervention in Syria. This research has concentrated on timespan of last decade (2011-2021) ant its method is analytic and descriptive.