During the
Williamite War in Ireland in the 1690s, the 4th Earl of Clancarty (also named Donough MacCarty) was captured, and his lands (including Blarney Castle) were confiscated by the
Williamites.
The castle was sold and changed hands several times — Sir
Richard Pyne, the
Lord Chief Justice of Ireland, owned it briefly — before being purchased in the early 18th century by Sir James St John Jefferyes, governor of Cork City.
[
en.wikipedia.org
In other words, it was stolen from the Irish. Give it back.