The Eldritch Accords, established by the Treaty of Zurich in 1919, are a set of agreements binding all major supernatural powers on Earth to this day. It established several important tenets:

• The supernatural "nations" are sovereign, and therefore any actions taken by their own members against those of other nations are matters of foreign interaction, as opposed to personal greivance
• Communication between sovereign nations of the supernatural shall first go through established diplomatic channels
• Rites and laws bind arbitration and allow for redress of grievance between disputantes of rival nations
• All supernatural nations are barred from invoking the mortal world to interfere in the disputes or affairs of supernatural nations
• To each supernatural nation is yielded its "domain"--those lesser supernatural powers and creatures of like kind and demeanor, who may not otherwise be signatories of the accords

(The lead-up: WWI, the Masquerade, wizards almost losing, then invoking the mortal authorities, etc)

(Peace, neutral ground, duels, weregilt, geographical reservations, etc)