Having played under EPA Playing Rules (or "old rules") in all prior seasons since 1977 (ruleset), the Aylesbury Invitation Pool League introduced World Rules into the league for the 2013-2014 season (ruleset).

The World Rules ruleset is part of the World Eightball Pool Federation (WEPF) founded in 1992 by England, Australia and New Zealand. It is an international pool governing body overseeing international (principally Commonwealth) tournaments and rankings. It was already 20 years old by the time the AIPL adopted World Rules.

WEPF competes for authority and membership with the World Pool-Billiard Association (WPA) which produces its own tournaments and slightly different rules under the game name Blackball which were intended would unify the various existing British-style rulesets (presumably also including the WEPF rules) although this has not yet happened. Blackball rules (ruleset) were first released on 29th September 2005 onto the WPA's web site with the new rules coming into force on 1st January 2006.

For many years different versions of rules caused unnecessary confusion amongst players and antagonism between self-appointed 'governing bodies' which had sprung up to administer 8ball pool. When the Blackball rules were first discussed and compiled, there were approximately 19 different sets of rules played in Great Britain alone, and the anticipated outcome of the new Blackball ruleset was that, given the recognition and support of the World Pool Association, national pool organisations would for the first time be able to unite under a single World structure and everyone could play the game to exactly the same rules.

World rules are no longer played at the professional level, since the International Professional Pool Association (IPA) swapped to WPA blackball rules in 2012 (again note this was before the AIPL adopted World Rules for their league), and around the world, World Rules are used less and less with more countries and leagues playing Blackball. However, the UK is one of the countries with the strongest remaining support for World Rules.

For the 2017 AIPL AGM, Amber Carter was asked to give a presentation on the differences between Blackball and World Rules, with a view on taking a vote at a future AGM about moving the AIPL onto Blackball rules. This presentation can be viewed or downloaded here.

It was also decided at the 2017 AGM that the league would organise some Blackball tournaments to help those who wanted to learn Blackball rules or learn the differences between Blackball and World Rules. Contact James Connor for more information (contact details on the committee page).

Update 18th July 2018: Blackball rules were voted to be introduced for the 2019-2020 season at the 2018 AGM.