Rules or laws?

I am going to buy a site to build a house in county Dublin. I found that some site just sale for the local need ( means for the Irish people living in Local area over 10 years). Is this Irish rules or by the law? What about the new new immigrants like me ? I have been living in Dublin for over 10 years, I am Irish citizen, so I do not have right to buy this kind of sites?
Any suggestions please?

You need to get an architect to advise you