authority competent to lay down qualifications for promotion, is also competent to change the qualifications. The rules defining qualifications and suitability for promotion are conditions of service and they can be changed retrospectively. This rule is however subject to a well recognised principle that the benefits acquired under the existing rules cannot be taken away by an amendment with retrospective effect, that is to say, there is no power to make such a rule under the proviso to Art.309 which affects or impairs vested rights. Therefore, unless it is specifically provided in the rules, the employees who are already promoted before the amendment of the rules cannot be reverted and their promotions cannot be recalled. In other words, such rules laying down qualifications for promotion made with retrospective effect must necessarily satisfy the test of Arts.14 and 16(1) of the Constitution : State of Mysore v. M.N.Krishna Murty, (1973) 2 SCR 575 : (AIR 1973 SC 1146), B.S.Yadav v. State of Punjab, (1981) 1 SCR 1024 : (AIR 1981 SC 561), State of Gujarat v. Ramanlal Keshavlal Soni, (1983) 2 SCR 287 : (AIR 1984 SC 161) and K.C.Arora v. State of Haryana, (1984) 3 SCR 623 : (1984 Lab IC 1015).”