(a) the common border between a Member State fully implementing the Schengen acquis and a Member State bound to apply the Schengen acquis in full, in conformity with its Act of Accession, but for which the relevant Council Decision authorising it to fully apply that acquis has not entered into force; (b) the common border between two Member States bound to apply the Schengen acquis in full, in conformity with their respective Acts of Accession, but for which the relevant Council Decision authorising them to fully apply that acquis has not yet entered into force