Minecraft Real Money Trading - Why is it Penal?

I once wanted to ask why real money trading on Minecraft servers is illegal, is it only illegal according to MC Eula or is there a law?

The server owners make the rules, most forbid it, because they do not want to be pulled in, if there's something in the direction of rip-off.

It is not punishable. There's no law against it. And even the Eula does not forbid it.

So, you have accepted the Eula when buying Minecraft, these Eula are legally part of the terms and conditions. In the Eula is anchored that you can buy with real money purchases no non-cosmetic advantage, by case, if you Z.b. Buy ingame money, you can most likely buy things that are probably not cosmetic.

If the server violates this, however, it may be legally warned due to disregard of the Terms, and forced to sign a declaration of omission, there's also usually a ban on opening a server also anchored.

You as a dealer usually nothing happens