This is what comes to my mind right now and probably what I'd say if I were to translate it. To me, 江湖规矩 is basically referring to the common practice in any field or area. There may be better ways of saying this in English. So this is just for your reference.

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Note added at 1 hr (2014-02-24 09:59:27 GMT)
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Oops, maybe it should be common practices (in the plural), as what comes before it is 有 (have), i.e. 'have common practices'.

左哈纳似乎可以归为clique

It's more or less a "house", after all.



1st RULE: You do not talk about FIGHT CLUB.

2nd RULE: You DO NOT talk about FIGHT CLUB.

3rd RULE: If someone says "stop" or goes limp, taps out the fight is over.

4th RULE: Only two guys to a fight.

5th RULE: One fight at a time.

6th RULE: No shirts, no shoes.

7th RULE: Fights will go on as long as they have to.

8th RULE: If this is your first night at FIGHT CLUB, you HAVE to fight.

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Note added at 1 hr (2014-02-24 10:40:20 GMT)
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It's slightly ambiguous whether these rules apply to individual Zurkhaneh or them as a whole. "Rules of the trade" may work in the latter case.

Depends on what you want to emphasise, of course. But the context is what Zurkhaneh/wushu does in society, and the term jianghu certainly conjures up the larger mythology around wushu, rather than just the sport itself. So you could use mystique to bring that element out.
"Code" is good, though, does almost the same thing, carries strong implications of an attractive moral order.

1. pugilistic should be added in front as a modifier regardless of which answer you use, in order to bring out the meaning of 江湖

2. Customs will capture the neutral meaning of 规矩; it is neither an honor or a taboo or any rule (house or otherwise) written in black and white, just some socially-accepted practices which have evolved over time within a particular subculture. The following two sentences illustrate my explanation:

Sports Illustrated
According to the pugilistic custom of the day, a round went on until someone was floored; after an interval the fighters would mutually agree to start again.

LA times article
Foreman became heavyweight champion of the world. He was strangely miscast for the role. In spite of the massive chest, the python-like arms, the left jab that looked like a telephone pole with a glove on it, there was a gentleness about George Foreman that defied pugilistic custom. It wasn't that he lacked the killer instinct, it was just that, well, he was the kind of guy who would bring roses to the guy he was going to knock out.

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Note added at 2 days5 hrs (2014-02-26 14:11:11 GMT)
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pugilistic custom, actually, without the "s"

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Note added at 5 days (2014-03-02 04:35:42 GMT) Post-grading
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If 江湖规矩 = code of honor, 江湖道义 = ？