Article 1: Establishment of an alliance.
(1) The countries participating in this Treaty (hereinafter referred to as the contracting parties) form an alliance, cooperate in the filing, retrieval and examination of applications for protection of inventions and creations, and provide specialized technical services. This alliance is called the International Patent Cooperation Alliance.
(2) Nothing in this Treaty shall be interpreted as impairing the rights of any national or resident of the Paris Convention for the Protection of Industrial Property.
Through the above explanation, the definition of member States is not emphasized in the treaty, and all countries in the alliance are contracting States (which can be understood as member States).