I don't know about this game, but I know in WoW you can get banned for trade ganking. All you have to do is screenshot the conversation and send it to a GM.
I don't know the rule here either, but that's besides the point.
Bioware shouldn't have to "protect" us from that. They've given us a "safe trade" way and a COD mailing system for a reason. We should use them to avoid situations like the OP described.