Ireland 's constitution was altered by referendum and its territorial claim to Northern Ireland was removed .
Arising from the Northern Ireland peace process , the matter was mutually resolved as part of the Good Friday Agreement in 1998 .
Northern Ireland 's constitution was altered by referendum and Northern Ireland 's territorial claim Northern Ireland   Ireland was removed .
Arising from the Northern Ireland peace process , the matter was mutually resolved as part of the Good Friday Agreement in 1998 .