Real World Trading, by our enforced rule definition, is trading something in BC for something that is out of BC through use of something the game does not provide. By this definition, it is entirely fine to buy items from administrators as we create the game, thus provide the service. However, buying items from other players is not being provided by the game (or its staff). Therefore, you are Real World Trading.
The rule is there for your safety and your safety alone. By enforcing the rule, it might help prevent it from happening again. Unlike what peacelover (who has absolutely no idea what he's talking about and is virtually speaking in three year old english) thinks, it actually is quite common that this happens. RWT is just a new and easier method of scamming, because the player will freely give you the items, though with the thought that he/she is getting a new item that they purchased. In essence, to give a stronger example than Zero's, it's basically "I'll sell you this item, but I want you to give me the money first then when I get the money I'll trade it". You wouldn't trade an item unless it's on the same window, so why would you RWT.
If you have questions, MSN. I decide on my rules carefully, I'll gladly explain them.