Holy See of the East the Church of the East after the Coonan Cross Oath and joined the Church of Antioch also claims the title of the Holy See of the East, since St. Thomas is also the founder of this churches. The Malankara Orthodox Syrian Church which evolved out of the Malankara Church as a part of the Oriental Orthodox Churches claims the title of the Catholicos of the East and the Holy Apostolic See of St. Thomas. The Malankara Syrian Catholic Church which evolved from the Malankara Church as a part of the Eastern Catholic Church in full communion with the Holy See
Foreign relations of the Holy See Holy See, not to Vatican City State. It is the Holy See that establishes treaties and concordats with other sovereign entities and likewise, generally, it is the Holy See that participates in international organizations, with the exception of those dealing with technical matters of clearly territorial character, such as: Under the terms of the Lateran Treaty, the Holy See has extraterritorial authority over various sites in Rome and two Italian sites outside of Rome, including the Pontifical Palace at Castel Gandolfo. The same authority is extended under international law over the Apostolic Nunciature of the Holy See in a foreign