You do not have to have a criminal conviction to be considered a risk.  It can relate to  any number of things,

IE:  Credit rating,  Known Associates, Communication links  etc etc etc etc etc..................

Ebay are no obliged to tell you the reason your account has been restricted, and in some instances it can actually be illegal for them to divulge such information to you.

If you intend making threats of or instigating legal action against ebay, then I suggest you  do it through a legal professional, and not carrying on on a public forum