I kind of agree with Rob-hin here a bit. If this friend of yours is going to only be a disruption to your game all of the time then a) say it to his face that this time during this campaign there are rules and limitations as to what they can do with their characters...
...or pregenerate each of your players characters (excluding their attributes, skills etc). E.g give your friend a fighter character and advise him exactly what the character is about, the characters history, the characters alignment, the characters racial enemies if any etc. So therefore forcing your mate to play the character but in the way that you have already built in place for them to be able to play it....
...another idea that springs to mind is play the "alignment card". Basically state at the start of the game that everyones character has be compatible.
In other words if the players do not play their characters to a certain alignment (which you have assigned their character) then the consequences will be bad for them....I have had situations like this where players have gone off on another tangent and I have bluntly stated that if they continue down this bath a) the people in the surrounding city will hunt him down b) his own party will turn on him and nullify if not kill his character due to his eratic behaviour or c) everyone in the party ignores his behaviour and so do all the npc's in the game foprcing him to "play ball" with the rest of the party.
I have had to "accidentally" kill some annoying characters sometimes...basically if I know someone is being annoying in the group and pulling the enjoyment of the game down I take the "DM's fair encounter" limitation off of anything that encounters this character and all of a sudden he is found to have a very large "string of bad luck" so to speak....to teach a lesson there is nothing better than making the enemy focus their attention on this players time and time again....he'll realise after a while that playing an unconscious character that requires healing for over 50% of each session is not really that fun...
