Solicitor Brian O'Donnell has been given until 5pm tomorrow evening to vacate the Gorse Hill mansion in south Dublin.
The High Court earlier granted a trespass injunction to Bank of Ireland for the property, which is at the centre of a row over a €70m debt.
Mr O'Donnell has told the Land League he is "astonished" by the ruling and is seeking an immediate appeal.
Mr Justice Brian McGovern told Mr O'Donnell that he 'is a trespasser' and must vacate the Gorse Hill property.
The Judge said Mr O'Donnell and his wife Mary Patricia do not own the house - that they live in the UK and flew in to 'frustrate' the attempts by the bank to take possession of the Killiney property.
Mr O'Donnell requested a stay of six months, but has been told he has until 5pm tomorrow to get his affairs in order and leave.
The solicitor's representatives have indicated he will be appealing the ruling.
Mr O'Donnell has left the Four Courts to go to the Court of Appeal in an attempt to have it heard.