6. The Authority must delete from the Register—E+W
(a)any ROC which has been revoked by it,
(b)any ROC which has been produced to it under article 7(2),
(c)any ROC which is no longer eligible to be produced to it under article 7(2),
(d)any ROC which it is asked to delete from the Register by the registered holder of the ROC, or
(e)any ROC which has been (according to the Northern Ireland authority) produced to the Northern Ireland authority by a Northern Ireland supplier under a NIRO Order,
and after a ROC is so deleted, it cannot be produced to the Authority under article 7(2).