To understand Article 102 of the UN Charter, we first have to understand that the UN Charter is the treaty (an intergovernmental agreement between States) that constituted the United Nations in 1945. It is legally binding upon the contracting States, and it so happens that virtually every country in the world is a member of the UN and therefore legally bound by the Charter.
Article 102 is the first article of Chapter 26:
CHAPTER XVI: MISCELLANEOUS PROVISIONS
Every treaty and every international agreement entered into by any Member of the United Nations after the present Charter comes into force shall as soon as possible be registered with the Secretariat and published by it.
No party to any such treaty or international agreement which has not been registered in accordance with the provisions of paragraph 1 of this Article may invoke that treaty or agreement before any organ of the United Nations.
In the Charter of the League of Nations, a treaty had to be registered to enter into force, but in the UN Charter a treaty (or international agreement – both expressions are used to ensure broad coverage) can enter into force without being registered. However, the UN Member States have undertaken the legal obligation to register their treaties and there is an incentive (or rather a penalty) if a treaty is filed: only registered treaties can be invoked before the UN Organs, including the Security Council and the International Court of Justice.
ARTICLE 102 OF THE UN CHARTER APPLIED TO THE EUCLID TREATIES
Like the United Nations, EUCLID (Euclid University) is an intergovernmental organization constituted with a Charter. However, there is also an obvious in the intention and method of the States since one is a universal organization with broad powers established in 1945 (the UN) and the other is a specialized organization with a specific background and defined with a less formal treaty process. One thing is sure, any intergovernmental established by treaty (amazingly, there are a few not established by treaty!) should have its constitutive treaty (charter or charta) processed under the terms of Article 102. The Article says that all the States involved should in theory do the filing, but in practice, a well-written treaty will designate a State (or organization) entrusted with the task, called depositary.
In the case of the EUCLID treaties, the initial formal filing was done by the States, but the UN Secretariat, having received the instructions of the States to proceed with the registration, opted to follow the practice of the UN Secretariat and to get the actual registration coordinated with the depositary, in this case the EUCLID Secretary General.