I've been to a number of forums in my time and everyone polices them in vague and inconsistant ways. Here is a forum that seems to have found a very definitive way of handling threads that break rules.
They post the rules somewhere and number them. (scroll down)
Then they site the infraction. IOW, thread close-------> see rule #10. (they link to rule #10)
Seems very clean, neat and tidy!