List of users who are not allowed to track local user's presence. null is returned until PresenceAccessControlRulesChanged or PresenceAccessControlPolicyChanged handler is assigned. In order to receive a list of allowed presence watchers subscribe to PresenceAccessControlRulesChanged or PresenceAccessControlPolicyChanged first and wait for events.

public ReadOnlyCollection<PresenceWatcher> BlockedWatchers { get; }