All the provisions of the Charter of the Collective Security Treaty Organization (CSTO) apply to Armenia, as a CSTO member, and in case of a military strike against 
Armenia, these norms will come into force, director general of the Institute for Caspian Cooperation Sergei Mikheev said when commenting on Azerbaijan’s threats to use force against Armenia and Nagorno Karabakh.
However, as he noted during Moscow-Yerevan spacebridge, Karbakh positions itself as an independent state and not as part of Armenia, and, therefore, it’s beyond the CSTO jurisdiction, according to Armenia Today.
For his part, head of the analytical center at MGIMO Institute of International Studies Andrey Kazantsev commented on Armenia’s decision to join the Customs Union, what, in his opinion, was a strategic move. “The CSTO membership and the Organization’s balancing role in the South Caucasus are of great value for Armenia,” he said.
Meanwhile, according to Novosti Armenia, representative of the CSTO Secretariat, professors Igor Panarin, said that all issues are being resolved within the CSTO in a balanced way.
The Collective Security Treaty Organization is an intergovernmental military alliance which was signed on May 15, 1992. The CSTO employs a “rotating presidency” system in which the country leading the CSTO alternates every year.
Source; PanARMENIAN.Net
The Collective Security Treaty Organization, formed under the framework of the Commonwealth of Independent States, serves as a mutual defense alliance among Russia, Armenia, Belarus, Kazakhstan, Kyrgyzstan, and Tajikistan. The Collective Security Treaty (CST) was signed on May 15, 1992 for five-year term, with the possibility of prolongation. On December 2, 2004 the General Assembly of the United Nations adopted the Resolution to grant the observer status to the Collective Security Treaty Organization in the General Assembly of the United Nations. The goal of the Collective Security Treaty Organization is to strengthen peace and international and regional security and stability and to ensure collective protection of independence, territorial integrity and sovereignty of Member States, in the attainment of which Member States shall give priority to political methods. On February 4, 2009, the CSTO leaders approved formation of Collective Rapid Reaction Force (RRF).