thank god they are stupid enough to not ban IP or hw
Not because they're not stupid, but if you really wanna play again and don't want to hack anymore they give you the chance for a new start (my thoughts)
So far I know a friend of mine bought a russian key which you will have to install MW3 russia, you simply can put the language back to english and play world wide. But it requires a different installation + russian IP.
Saying I'm not experienced with this, only googled a little and found this.