That indeed is in the rule book
Read up on it
http://www.platform11.org/passenger_info/legal.php
Question Cork Bray, can I break my journey in Blackrock it would appear you can since you have a intercity ticket
Point to note is the conditions of carriage are conditions, there are not law so it would be interesting to see how IE could apply them against you when they contradict SI 109 and the Rail Safety Act 2005 sec 132