So many overseas posters with views on JAA licences.....
A JAA licence carries an entry if that states that "the privileges of the this licence may be excercised at night" if the holder has obtained a night qualification. If they do not hold the night qualification then they can't fly at night. To gain the night qualification they have to do five hours of night flying training. Unde EASA it once again becomes a night rating but the process is the same.
To hold a JAA IR you must hold a night qualification unless you are colour blind and cant gain a night qualification and in very rare cases have been granted a DAY ONLY IR.
Holding a JAA IR also exempts you from the night currency requirements for take off and landings.