User blog comment:Nelraye/Lore Discussion: Riot, what happened?/@comment-5266525-20140221175031

As far as I'm concerned, Riot is trying to remove all references to the in-universe League of Legends, which makes me a little sad as it's a step back to DotA where most of the characters are independent and have no interaction with one another. The League functioned as a good way to bring these otherwise separate characters together in a visible way.

I don't think they mean to say that the League no longer exists at all, though (I mean, some of the listed friends on some of the champion pages wouldn't make too much sense if it didn't).

That being said, the only requirement that you really needed to join the League as far as I could tell was just to demand entry and not be put off by the Observation and Judgement. A lot of the older champions didn't seem to have a real reason to be there either (Twisted Fate, old Sivir, etc).