At its 1986 Ard Fheis , Sinn FÃ in changed its and constitution to allow its members to sit in the Dublin parliament ( Leinster House\/D Ã il Ã ireann ) . At its 1986 Ard Fheis , Sinn FÃ in delegates passed a resolution to amend the rules and constitution that would allow its members to sit in the Dublin parliament ( Leinster House\/D Ã il Ã ireann ) .