Please post your question in the Michael Kors Authentication thread with photos of the bag. This forum is only for reporting counterfeit
Coach products.
http://forum.purseblog.com/threads/authenticate-this-michael-kors.895098/
Selling counterfeit brand-name items that are protected by US trademark and copyright laws IS against US Federal law. However, the FBI and Homeland Security probably have other things on their mind at the moment. But there are also local laws against Fraud and Theft By Deception that are enforced by local police departments. So yes, if you sold a faKe, you could be reported. And if you didn't buy it directly from the brand's own stores or retail partners like major department stores, there's
always a chance that it's fake.
If you didn't take clear photos of the bag before you sold it, I suggest you give the buyer a refund, take the bag back making sure it's in the same condition as when you sold it, and post a clear set of photos at the Michael Kors forum to authenticate it before trying to sell it again.
And PLEASE read the first "stickied" post in any forums that you post in if there is one, and make sure you're asking your question in the right place.
Does the post by another member that you included in your question have anything at all to do with your situation? If not, you shouldn't use it in your post.