Gold buying, it's kind of like speeding isn't it really. Despite it being wrong, bad for everyone as a whole, people do it and the world doesn't end. Now and again the odd person is caught and a penalty is handed out by the government via the courts, depending on how bad it was the worse the fine. As long as it's kept under control civilization, or at least the free ways, won't collapse.

Putting RMT in these games though 'as law' is pretty much the same as your local government saying 'SPEED ALL YOU WANT, JUST PAY EXTRA' We'll just use the extra revenue to build more roads when the old ones collapse from the strain and wreckage. Strangely enough few real life judicial systems have been keen to carry out this... logic.

Or easier: think of it is your local cops legalizing the mafia in return for some cash, ignoring why their acts where made illegal in the first place.

Just hand out a few large scale public announced bans to the BUYERS as well as the sellers. It would die away in weeks. Take the pressure of those who don't want to cheat this way but feel obliged too by those who do - these games might not be competitive, but they definitely are comparative. Everyone knows that buyers don't get in trouble.