The rules committee members for pool and billiards players work very hard to ensure clarity and explicit explanations for the rules of competition. Even so, there are always many areas where interpretations can be applied. It's the Clinton excuse, "It depends on what the meaning of the word 'is' is." This area is ripe for abuse by the pool hustler. It is the ongoing, ready-to-dispute attitude of nit-picking and quibbling is what makes this sharking trick work.
The hustler must invest a significant amount of preparation and study into every set of rules at the local, national, and international level. Being a gamesman, the intricacies of rules have a natural fascination. He is greatly involved with studying the whole concepts, intentions, down through the microscopic levels. (This fascination of micro definitions is why some people become lawyers – and then politicians.)
There are levels of rules expertise qualities. At the low end, you find the dilettante dabbler. This person attempts to appear to be an expert rules master. But because he is a dilettante, he won’t have put in the necessary study time. At this level, the wannabe expert happily misinterprets the rules and gets many of them just plain wrong.
He can even be capable of making up rules on the spot. He covers up his ignorance and half-knowledge by increasing the strength of his vehement declarations of expertise. He can get downright loud when his rulings are challenged (the louder, the more unsure he is about the truth of his judgments).
In action, the hustler’s eagle eye closely watches your every movement starting when you come into the playing area. He pays close attention to all of your actions. Every body movement, shift and adjustment is judged against every possible interpretation of the game rules.
Another thing he has to verify if whether you are knowledgeable about all the rules. This can be verified with a few test questions, such as, “Are we playing APA or BCA rules?” If you express some knowledge, he may probe further – or assume you have a layman’s knowledge.
From that basis, he starts closely monitoring your every action from racking to shooting. On your first violation (or his perceived observation of violation), he throws himself into the declaration of your “error” – with great enthusiasm. Much depends on the seeming certainty of his knowledge.
His first exuberance is designed to catch you unawares. It is intended to disrupt your rhythm and has the bonus of completely removing your attention on the game to his complaint. He might be right or wrong – it really doesn’t matter.
If you argue about it and somehow win, you return to the game feeling irritated and upset - not a good mind-set for competitive situations. If this is followed by poor playing, you get even further upset with yourself. Even if he is wrong and you prove it, that doesn’t change the affect he has made on your playing attitude.
After that first massive distraction, he probably implements the "constant reminder" tactic. Whenever you are setting up for a shot, he "helpfully" reminds you of a potential rule violation that you must be careful not to commit. This constant intrusion into your attention on playing the game is a major distraction to your playing rhythm. All of this benefits him and hurts you.
When you come across such an opponent, every time he calls out the penalty, insist that he get out the rule book and show you the exact wording. Do this even when you know you have committed the violation. It never hurts to keep him concentrating on looking up rules instead of playing his best game.
If he declares a violation you are unfamiliar with, force him through the proof process. You might learn something. Use him to educate yourself about some of the more obscure rulings. You might pick up a tip or two to use against future competitors.
If he doesn't have a rule book, dramatically express shock and dismay. Ask him, "How can you call a foul if you don't even have the rules with you? What's the matter with you?" Mock him for the rest of the match. Every once in a while, catch his eye and sadly shake your head.