Universe-Travelling Restriction Act 1999
The Universe-Travelling Restriction Act 1999 is a book written by the founders of the current society of the Eternal Universe. It is the basis for most of their beliefs - particularly the belief that extra-dimensional travel into or out of the Eternal Universe would result in the collapse of society and unending chaos. The Dark Universe is given as an example of this in the book.
As its title would suggest, it was written in the Eternal Universe in Year 1999 - not 1999 as corresponding to Earthen calendars, but the 1999th year their universe existed. Breakout, the EU's version of Blackout, is credited as an author. The rules laid down by the book are enforced by a secretive society in the EU named "The Upholders of the Eternal Vow".