That's so stupid, if its labeled (Fan art) why should it be illegal ,you're showing that it's not yours and supporting that artist or whatever cause you're were inspired to draw a peice of their work lol.
I don't understand.

There's also people who are arguing that it won't be illegal.
http://ryanbrony765.deviantart.com/journal/To-those-of-you-who-are-afraid-of-the-TPP-596376399

I'm pretty sure posting fan-art won't be illegal, but selling lot's of it... I don't know... politics is confusing. I'm pretty sure copyright owners wouldn't really object or go after people who make fan art cause it's like free advertising.