If you are an Advanced Trainer, Master Trainer, an Elite Four member, or a Champion, you are now able to see the Legendary Isles you couldn't see before. This means you can now battle the pokemon in those places and even the legendaries for experience points. BUT. You are not able to capture the legendary, and you can't post a lot of posts here.
Also, keep in mind the legendaries are at least level 50 so please, keep this in mind if you are posting a battle against them.
But again, if you are one of those types of trainers, you've probably earned it.