what does amir mean when he says "Afghans cherish custom but abhor rules"?

The Afghans are very independent people. Thye cherish their identity and customs, but they will fight to the death if anyone attempts to impose rules on them. Examples of this would be their response to the British in the early 1900's, and their response to the Russians in the 1980's. In context, Amir is also describing the art of kite fighting..... no rules..... and anything goes. It's a battle, period.