International

I made the mistake of Googling for Foundations of International Law.
Kinda complicated, it turns out. I did take away from it the brocard (maxim)
Pacta sunt servanda.

French authors make much of the Treaties of Westphalia (1648), because they
are seen as establishing the modern conception of the State and its territorial integrity.
In effect, these led to the eventual dismantling of the Holy German Empire into separate
Princely States(1806) - something Nazi Germany later complained about - but also the
recognition of the sovereignty of states, and religious freedom in statecraft.

English language authors make much of the United Nations and its Charter,
and its major institutions - the Security Council - and the International Court
of Justice (post World War 2). In effect, a going beyond of Westphalia in that
regional interest and alliances are now part of the game.

Candidate Trump did characterize the UN as out of date. To put a different twist
on it, I would say the UN does seem to manifest a certain crispation (rigor mortis)
in its formal organization. Looks like an eternity of the major 5 on the Security
Council.

There is a motion to outlaw nuclear weapons altogether to be voted  on Wednesday.
This is one instance where North Korea and the Us appear to be playing off each other.

http://droit.univ-lille2.fr/fileadmin/user_upload/enseignants/lavenue/DIP/dip_1_4.pdf

http://agora.qc.ca/Documents/Droit_international--Les_traites_de_Westphalie__une_revolution_du_droit_international_par_Karel_Vereycken