Why yes Virginia, you can sue RMTs...
We all know that RMT and their bots are a significant and negative threat to our game. Just the mere fact that related permanent account bans averaging up to 25,000 a week seem to be a regular thing is enough to tell us that.
Until now, the common wisdom is that SE can't really do much to sue these people to stop them. I believe that may have changed, or at least the common wisdom may have to be adjusted.
The folks behind League of Legends won $10 million in a case against a bot/cheating service called "LeagueSharp", in addition to granting Riot (LoL creators) control over LeagueSharps websites.
See the links;
Gamezone story about LoL suing LeagueSharp
Engadget story about the lawsuit.
It seems that RIOT may have got creative and used the Digital Millenium copyright Act to sue because there was circumvention of the digital protection of their software.
It may not be possible for SE to use the same grounds against the various RMT organizations that plague us, but this does show that it's possible for game operators and creators to go after these parasites.