I've just finished reading The Nomos of the Earth in the International Law of the Jus Publicum Europeaeum. Unfortunately the English edition is not very easy to find. It's published by Telos Press Publishing (New York NY 2006: ISBN 978-0-914386-30-8). I found it on Amazon.com, but it's not available on Amazon.co.uk, and it could only be delivered to me via a UK address, not directly to Turkey.
A remarkable book. Many thoughts inspired. Some brief non-theoretical thoughts for now.
I learned for the first time that the the French Foreign Minister Aristide Briande proposed a European Union for the first time in the late 1920s.
Belgian neutrality was a cornerstone of the European inter-state system until Germnay violate it in 1914, leaving the question of how the German government of time could have thought it was worth invading Belgium with the inevitable result of alienating European public opinion. This act certainly had a major influence on the British Liberal cabinet of the time which was not eager to enter into a general European war.
The League of Nations recognised the western hemisphere as off bounds, confirming the Monroe doctrine in which the US had forbidden foreign intervention in the Americas. This recognition was despite the the non-membership of the US in the League.
Schmitt a German Catholic Nationalist has no doubt whatsover that not only was the Ottoman Empire part of the European Concert of States, but that it was part of the European legal and political space in the fullest way. This despite the nostalgic tone Schmitt adopts towards the Crusades and the era in which he believes Europe/Christendom established political institutions as a barrier against the premature appearance of the anti-Christ, and excluded all non-Christians from international law. Schmitt's suggestion that the state system was a a barrier against the Anti-Christ is not an abstract Catholic claim, it is a judgement of what the legal and political foundations of Empire and Papacy were at that time. Schmitt is suspicious of the abstractions of Augustine and Aquinas, it is the concrete choice of enemies that he he focuses on, following his analysis in The Concept of the Political.