A further comment removed: 

 "The only difference is that those born in the Republic who are Irish Citizen by birth, achieve this citizenship automatically; those from Northern Ireland need to specifically declare themselves to be Irish Citizens in order to be so, unless they have parents or grandparents who are already Irish Citizens. Those from Northern Ireland have the exact entitlement to Irish Citizenship as those born in any other part of Ireland." 

 This was true under the pre-1999 laws, however now the key question as to whether one is a 'full' Irish citizen at birth or just 'entitled' to be an Irish citizen is based not on whether one is born in the ROI or Northern Ireland, but on whether one has another citizenship at birth.    

 Most people born in Northern Ireland do have another citizenship (British) but the law applies equally to those born in the Republic of Ireland who acquire British or another citizenship (by descent) at the time of birth.    It's a grey area if the 'other' citizenship requires registration, in the case of Australia, for example. 

 All that said, the distinction between someone who is 'entitled' to be an Irish citizen and an Irish citizen proper is a grey area.    It is unlikely that it will be tested in the Irish courts, however it may become an issue in a foreign court (if entitlement to citizenship of another country depends on not having Irish citizenship).    One one construction, the distiction is merely a political statement that certain Irish citizens will not be treated as having that citizenship unless they wish to.