If you are an Irish citizen getting married outside of Ireland, the legal standing of your marriage may be governed by the laws of the country in which you marry. In particular, a church marriage abroad can be a religious ceremony with no legal effect.
You must take care to comply with all legal requirements of the country in which your marriage ceremony will take place. If you do, the marriage will be recognised as legally valid in Ireland. Alternatively, you could consider a civil marriage ceremony in Ireland, which would be legally binding prior to a wedding celebration abroad.