Following the events of Legends, the Justice League was revitalised (to say the least) and from its beginnings as simply a new version of the JLA, was transformed into a United Nations sponsored world-wide group of superheroes with embassies in most major countries.
Thing is, there was already a group with the same mandate, one which had a more international membership than the fledgling JLA/I. Sure, the League had a more interplanetary membership (with J'onn J'onzz and Mr Miracle) but the Global Guardians were already in place and as we saw last week, represented more of the globe than the League.
Still, politics being what they are, with the UN sanctioning the League, there was no need for the Guardians.
Justice League International #9 featured the first of several back-up appearances of the Guardians as they dealt with the closure of the Dome and while some, such as Belphegor and Dr Mist were quite philosophical about the affair, the Irish hero Jack O'Lantern was definitely not.