I will have to google and see if I can find the article. But I saw an official statement from lucasarts not long after their acquisition by Disney. It stated that they had appointed a team essentially in charge of the Star Wars cannon. And because they did not want episodes VII-IX having to follow the story of the EU, they determined that anything in the books, comics, or videogames is no longer considered "cannon" in the Star Wars universe. Basically if it happened in the movies for episodes I-VI or in the animated series (I.e. Clone wars) then it counts. If it's EU in terms of comics, novels, or videogames, it may or may not count.