Generalist rules, rule.

So your RPG states that in your setting, no guns are allowed. What do you do when a player's character brings in a flamethrower? Immediately you know that they aren't allowed either, so what do you do? You add "No flamethrowers" to the rules list. There, all good! Until someone else comes along with a laser.

We had a problem with players having their cats be carried around alive, acll over the game by eagles and falcons until we finally put an end to this with a rule: No carrying your cats around by eagle or falcon.

It only added to the clutter.

Looking in our rules, we saw that they were in fact getting quite long. And it was totally unnecessary. What did we do? We filed that falcon rule under rulebreaks that break the "realism" rule, removed it from the rules directly except as a link out to a guide.

Write your rules to be broadly reaching wherever you can! Instead of "No guns, no flame throwers, no lasers, no missiles, no bows and arrows..." say, "No weapons beyond X level of technology" or "No projectile weapons" based on the setting of your game you will be able to determine the parameters better than I can as an outsider. Be as broad as you can.

A clue that your rules are not broad enough is that you have been adding new ones frequently and your rules list is getting quite long. chances are that if you look back you might find that a given rule break is already covered under an existing rule. "Play within the realism of the setting" is a nice one that covers plenty. and remember: prospective members tend to find long rules lists intimidating and confusing. So! Keep your rules as broad as you can and it's likely you can also keep them short and sweet.