29. It is now a well settled principle of law that the conditions of service of an employee can be laid down by the State in the following manner:

(a) By framing a rule under proviso to Article 309 of the Constitution of India.

(b) By framing a rule under the provisions of any statute governing the services the employees.

(c) By reason of executive instructions by the State of Bihar in exercise of its power conferred upon it under Article 162 of the Constitution of India.

30. It is also well settled by reason of various decision of the Supreme Court of India including Santram’s case and Joseph’s case (supra) that any executive instruction issued by the State shall have the force of law; but the same shall be subject to the provisions of any legislative Act or any rule framed either Article 309 of the Constitution of India or under the provisions of any statute.

31. It is further well settled that executive instructions would operate in the field uncovered by the rules framed under Article 309 of the Constitution of India or under the provisions of any statute. But the Government cannot alter the conditions of service prescribed by the rules by issuing an administrative instruction (see State of Haryana v. Shamsher Jang Shukla (MANU/SC/0597/1972 : A.I.R. 1972 S.C. 1546.)32. It is further well settled that whereas a rule made under Article 309 of the Constitution of India may have a retrospective effect but an executive instruction cannot operate retrospectively. It is also well settled that even in a case where a rule was framed after complying with all the conditions of framing a rule in terms of Article 309 of the Constitution of India, such a rule shall have the force of law irrespective of the fact as to whether it has been termed as a rule or not.