British citizens with Irish parents are entitled to hold Irish passports, and those with Irish grandparents can also apply.Anyone born before 2005 in Northern Ireland, the only part of the United Kingdom that shares a land border with another country, is entitled to Irish citizenship, though there are some restrictions for those born after that date.
Are there implications for people working or studying in the UK?
The withdrawal of the UK from the EU will take a considerable amount of time (at least two years, it is expected) and negotiation, during which the UK will remain a member state with no changes to current freedoms for EU citizens to travel and work between Ireland and the UK. Every effort will be made to minimize any changes to these arrangements and in any event people will be fully informed of any changes eventually made.
More info on :www.dfa.ie/irelanduk-citizenshipandpassports