The National Driver Licensing Service (NDLS) is the statutory responsibility of the Road Safety Authority (RSA).
I can however clarify that in the specific case of emigrants, it is important to remember that EU law requires that people who apply for a driving licence in a Member State must be normally resident in that country. The term ‘normally resident’ is generally considered as the place where a person lives for at least 185 days in each calendar year, because of personal and work ties. Where a person is living abroad and working on a fixed term contract or attending a college or university, they can be thought of as resident in Ireland providing they have personal ties here, even though they may spend much less than half of a given year in the country.
The RSA has developed procedures to allow people who are abroad on such a basis but normally resident in Ireland to apply for renewal of their driving licence without having to return to appear in person at an NDLS centre. This includes providing two passport-size photographs signed on the back. Full details of this arrangement can be obtained from the RSA.
People who are no longer normally resident in Ireland cannot renew a driving licence here. They should do that in their country of residence.