While World's End has very few strictly enforced rules, there are a few laws that exist, mostly for the safety of the inhabitants.
Wide-ranging magical powers are automatically dampened to short-range levels, and the magic involved is drained by the environment. This acts to protect the area from significant damage (say, from a visiting god deciding to fireball the entire town), and limits - but does not negate - the ability of combatants to wage war with magical powers. Attempts to override this restriction or gross exploitation of this feature may annoy the Mayor.
Heavy weaponry and sustained use of firearms, high explosives, beam weaponry, and similar, likewise, will be tolerated until it begins to cause significant environmental damage, at which point it runs the risk of annoying the Mayor.
World's End is a stabilized pocket dimension that exists via the benevolence of the Mayor. This means, first and foremost, that it is strongly resistant to attempts to disrupt its internal fabric, and second, that attempts to do so will annoy the Mayor.
As a general rule, attempting to annihilate the populace en masse, or destroy significant sections of the territory, will annoy the Mayor.
Anything that annoys the Mayor may result in forfeiture, incarceration, incapacitation, dimensional banishment, violation, consumption, annihilation, and/or forcible rehabilitation and repurposing.