Full Idea
Kant developed the social contract theory into an international and cosmopolitan idea.
Gist of Idea
Kant made the social contract international and cosmopolitan
Source
report of Immanuel Kant (Perpetual Peace [1795]) by Johanna Oksala - Political Philosophy: all that matters Ch.6
Book Reference
Oksala,Johanna: 'Political Philosophy' [Hodder and Stoughton 2013], p.73
A Reaction
That is, the contract both operates between states, and rises above them. I found this idea rather thrilling when I first met it (listening to Onora O'Neill). But then I remain a child of the Englightenment.