William Ennis says that William III, Oscar Wilde, and Roger Casement would not have had the right to marry in Ireland.
Of these three, two were, in fact, married: Oscar Wilde (to Constance Lloyd in 1881); and King William (to Mary Stuart in 1677).
While these unions took place outside of Ireland, there is no reason to believe that they would not have been allowed to celebrate their marriages on this island.
REV PATRICK G BURKE
Castlecomer, Co Kilkenny