Far as I have gleaned from various reports and news articles about fan art, it really isn't legally kosher, but no one can initiate legal action except the copyright or IP owner ( creator / company / estate of creator / etc ). Even in Japan, where the fan works community is huge, there is a tolerance by owners of the IP to the extent that some fan art may be created for sale as long as unit numbers do not exceed a certain amount or value. Very generous, but the weight of the law still can be brought to bear on any fan works, if the IP holders so deem necessary.

Eternal Hobbyist