History of Global Constitutionalism

Global constitutionalism is the branch of constitutional law that studies the creation of rules that are binding to all world nations.
The Charter of the United Nations can be considered the first document of global constitutional law, because it is the foundational treaty of the United Nations, the largest intergovernmental organization in history.
As a charter, it is a constituent treaty, and all members are bound by its articles. Furthermore, Article 103 of the Charter states that obligations to the United Nations prevail over all other treaty obligations.
The constitutional goals of the Charter are confirmed by its opening words (‘We the Peoples of the UNs’) which are modelled on the preamble of the Constitution of the United States.
In 1962, Sir Humphrey Waldock, at one time President of the International Court of Justice, stated in his Hague Lectures: “The Charter, like the Covenant of the League of Nations, is technically a multilateral treaty between States. But the Charter proclaims itself, more openly than the Covenant, to be the Constitution of an Organization and not merely a treaty (Waldock, General Course on Public International Law, 106 (II 1962).
However, the United Nations is an international organization, not a government, and therefore the Charter is strictly defined as a foundation treaty, not a “constitution”.
The first three articles of the Constitution of the United States entrench the doctrine of the separation of powers, whereby the federal government is divided into three branches: the legislative, consisting of the bicameral Congress; the executive, consisting of the President; and the judicial, consisting of the Supreme Court and other federal courts. Articles Four, Five and Six entrench concepts of federalism, describing the rights and responsibilities of state governments and of the states in relationship to the federal government.
The first ten amendments are known collectively as the Bill of Rights, offering specific protections of individual liberty and justice and placing restrictions on the powers of government.
Dr. Francesco Stipo, President of the U.S. Association of the Club of Rome, was the first author to describe a global constitution based on the principle of separation of powers, and to apply the federalist model to the United Nations, in his book “World Federalist Manifesto, Guide to Political Globalization“).
Dr. Stipo presented a model of world confederation divided into international legislative, executive, judicial and financial branches. In his view, the “world government shall share the authority with Member States, in a way that both are sovereign within their respective sphere of competence. The world confederation should reflect the political and economic balances of world nations” (Stipo, Francesco “World Federalist Manifesto. Guide to Political Globalization” April 10, 2007).
To transform the U.N. Charter in a global constitution, Dr. Stipo proposed to unify the budget and administration of the different UN agencies (such as FAO, ICAO, WHO) under the direction of the Secretary General and have one budget, one General Assembly, and one single contribution for the entire United Nations System  (interview in International Focus Magazine, on May 7, 2018). The specialized agencies would assume the juridical nature of international ministries or international departments, becoming internal divisions of the United Nations, under the direction of the Secretary General (Wikipedia).
In McCulloch v. Maryland, U.S. Chief Justice Marshall enounced the implied powers doctrine: “Let the end be legitimate, let it be within the scope of the constitution, and all means which are appropriate, which are plainly adapted to that end, which are not prohibited, but consist with the letter and spirit of the constitution, are constitutional” (McCulloch v. Maryland, 17 U.S. 316), opening the case for a judicial interpretation of the UN Charter as a global constitution.
In fact, in the Reparation case, the International Court of Justice in holding that the United Nations had the capacity in international law to bring claims against a State for injury to its agents declared: “Under international law, the Organization must be deemed to have those powers which, though not expressly provided in the Charter, are conferred upon it by necessary implication as being essential to the performance of its duties” (Reparation for Injuries Suffered in the Service of the United Nations, 1949 I.C.J. 174, 182 (Advisory Opinion).
John Foster Dulles, representing the United States at San Francisco, stated with respect to the domestic jurisdiction clause (Article 2 (7)):
“What is needed is a principle that is sufficiently basic to guide the organization through the many years to come, and to permit of evolution according to what may, during those years, be the developing ideas and changing conditions of the world community . . . We in the United States have repeatedly given thanks that the framers of our Constitution did not attempt to be legalistic and to set up rigid lines of demarcation. We here will equally serve the cause of posterity if we adopt for the world organization a principle of simple language which is clear in intent and flexible in its application Statement before Comm. I/1, verbatim in N.Y. Times, June 16, 1945, at 9, col. 3).
The general interpretation is that the U.N. Charter is not a constitution but it may become a constitution by amendment or by interpretation in the future.