An organization that promotes competitive, usually team, amateur cue sports, most commonly pool, especially eight-ball and nine-ball , although there are also well-established snooker leagues. Some leagues, many of which are decades old, are entirely local and either informal or incorporated, and may use their own local rules or may have adopted more widely published rulesets, such as those of the WPA . Other leagues are organized on a multi-regional or even international level, and may be non-profit or for-profit enterprises, usually with their own fine-tuned rule books. Despite differences, the largest leagues are increasingly converging toward the WPA rules, with the exception of the APA /CPA, which retains rules much closer to US-style bar pool . At least four major pool leagues hold international championships in Las Vegas, Nevada annually (APA/CPA, BCAPL , VNEA and ACS /CCS). Some leagues also offer one-on-one tournaments, scotch doubles events, artistic pool competition, and other non-team activities. (See Category:Cue sports leagues for a listing of articles on various leagues.)