This link takes you to the latest edition of the official Laws of the Sport, Crystal Mark Third Edition. Here is a Summary of Amendments to the Second Edition  prepared by Nick Watkins, of the Victoria LBC, who is the Chair, National Officiating Committee for Bowls Canada.

Jack Length Clarification – 2011

Rule 23.5.1 of the new Laws of the Sport of Bowls, Crystal Mark 2nd Edition, 2011 gives National Authorities the discretion to change the minimum jack length from 23 m to 21 m.

After careful consideration, Bowls Canada Boulingrin, the National Authority for Canada, has decided to change the minimum jack length from 23 m to 21 m for all play in Canada.

This decision leads to a number of other changes to distances set out in the Laws, as further detailed in rules 23.5.1 to 23.5.3, and will necessitate changes to the positioning of “hog line markers” at clubs across the country.

For safety reasons in particular, an exemption will apply for the Pacific Indoor Bowls Club and the Qualicum Indoor venue, which may continue to use a minimum jack length of 23 m.