AFAIK the eruvim are not dictated by “high courts” (there is no “high court” at all), but are instead constructed and maintained by various Orthodox groups. Not all Orthodox groups agree about their propriety either, so the presence of an eruv doesn’t necessarily mean that it’s recognized.

(Also pedantic, but it’s not the entire city: there’s a Manhattan eruv that covers a large part of Manhattan, while Brooklyn, Queens, and the Bronx have separate smaller eruvim.)