When the Calendar Server reads an ACL, it uses the first ACE it encounters that either grants or denies access to the target. Thus, the ordering of an ACL is significant, and ACE strings should be ordered such that the more specific ones appear before the more general ones.
For example, suppose the first ACE in an ACL for the calendar jsmith:sports grants read access to all users. Then, Calendar Server encounters a second ACE that denies bjones read access to this calendar. In this case, Calendar Server grants bjones read access to this calendar and ignores the second ACE because it is a conflict. Therefore, to ensure that an access right for a specific user such as bjones is honored, the ACE for bjones should be positioned in the ACL before more global entries such as an ACE that applies to all users of a calendar.