Honour, Code of Conduct, etc.

[TEF]

There hasn't been an official rule against that ever, you're free to attack/kill people at the FC any time you want.

Finally, the Fight Club is not run by the Crew so it's not necessarily a rule, only a bit of common courtesy if you will (though I don't advise ruining it as many regulars will start to go after you).

Which is what I was hinting at there.

True. Although a lot of people will probably consider it lame to do.
Myself including, although again depending on the situation / person If someone always shoots @ FC, I wouldn't hesitate to shoot him myself when HE doesn't expect it. Although I haven't really been there in ages

Because you suck!