Is a question of whether or not an action is considered "cheating" in a game within the parameters of the law exchange? If not, which stack exchange site might help me with a question as to the game of billiards?
It is not.
Law Stack Exchange is for questions that involve the law. Questions about the rules of a game are simply off-topic as they do not have any legal aspect to them.
Board and Card Games pops up in my head, but I'm not sure if billiards is on-topic. You should check.
Apart from Board and Card Games, there is a remote chance that it could be on-topic for Philosophy, provided that you could reduce the matter to a logical inference (the question would be whether the inference is consistent with the game premises). Cheating is immoral, and ethics is a well-known branch of philosophy, which open up another way of framing the question.
Depends what you mean by cheating and what games you are talking about.
For sport (and board/card games), in general, questions about the rules "on the field" would be off-topic but questions about the conduct and structure of competitions would generally be fine - these take place within the legal framework of the country and cheating would be lawbreaking.
Indeed, there is a specific international tribunal which most jurisdictions recognise as a body that can handle mediations and arbitrations on this matter: the Court of Arbitration for Sport
Questions about or involving the application of (national or international) law or legal process or legal expertise to the realm of sports, are on-topic for Law Stack Exchange.
questions about the America's Cup yacht race series: the rules are (vigorously) arbitrated by a court in New York, involving a legal process and legal expertise, and are likely to be on-topic.
questions regarding appeals to the Court of Arbitration for Sport: these invoke and involve a legal process and legal expertise, and are likely to be on-topic.
questions about the (alleged or actual) crimes of a sportsperson (be they real or hypothetical): the sport is only tangential, while the question is clearly about some aspect of law, and are likely to be on-topic.
questions about laws and regulations, contracts and terms which apply to a game or games (e.g. casino gaming, live tournaments or online play of other games): these are similarly a question about aspects of law where the law happens to deal with games. However, check that they aren't already answered under more general terms.
Questions about the interpretation of a rule or law in a sport, board or card game, or other competitive environment is off-topic for Law Stack Exchange. However, it may well be on-topic for another Stack Exchange website, such as
Note that your question may straddle more than one SE site (it is potentially on-topic for both, to greater or lesser extent), or it may fall in the gap between two or several of them (it is on-topic for none/is off-topic for all). Specific queries about whether a given question is on-/off-topic, should be directed to the appropriate meta.