The salary and allowances payable to, and the other terms and conditions of service (including pension, gratuity and other retirement benefits) of, 1[the Presiding Officer of a Tribunal or the Chairperson of an Appellate Tribunal] shall be such as may be prescribed:
Provided that neither the salary and allowances nor the other terms and conditions of service of 2[the Presiding Officer of a Tribunal or the Chairperson of an Appellate Tribunal shall be varied to his] disadvantage after appointment.