On Saturday night, Sin Cara made a surprise run-in at AAA's Guerra de Titanes show. His name was shown on the big screen in the arena and he ended up being referred to by that name by the announcers as well. However, there's a potential problem with that.
For starters, WWE owns the Sin Cara trademark and he's currently under a 90-day non-compete clause which should have stopped him from making an appearance of this nature for AAA.
Now, it's possible that WWE has given him permission to use the name and make this appearance but that seems highly unlikely. However, it would be foolish of both Sin Cara and AAA to risk being sued by WWE as they're not going to take something like this lying down (it's also worth noting that Dave Meltzer has confirmed that he doesn't have the permission to use the name).
We'll have to wait and see what happens but it's fair to say that the man under the mask, Jorge Arias, could be in bug trouble if he's just decided to chance his luck with this surprise run in!