240. The Judges of the Supreme Court and of the several High Courts shall be entitled to such salaries and allowances and to such rights in respect of leave and pensions as may be determined by law: Provided that-
(a) the salaries of the Judges of High Courts shall not be less than those of the Ministers of Units concerned and the salaries of the Judges of the Supreme Court shall not be less than those of the Ministers of the Federation;
(b) neither the salary of a Judge nor his rights in respect of leave of absence or pension shall be varied to his disadvantage after his appointment.