1. The petitioners in Writ Petitions Nos. 511, 548 and 549 of 1960, were Sales Tax Officers Class II in the erstwhile State of Hyderabad and those in Writ Petitions Nos. 510 and 540 of 1960, Sales Tax Officers, Grade III, in the then State of Bombay. When three districts of the erstwhile State of Hyderabad and four districts of the State of Bombay became part of the now State1 of Mysore, which was formed on November 1, 1956, by the States Re - organisation Act, they were allotted under that Act for service in the new State of Mysore. They are now in the service of that State.

2. The civil service of the new State of Mysore consisted principally of persons who were before its formation, holding posts under the then States of Mysore, Hyderabad, Coorg, Madras and Bombay. The various services of which there was thus a concourse in the new State of Mysore, required integration, and for that purpose, that State made on May 25, 1957, a list recording the provisional determination of the relative seniority and classification of two classes of its civil servants in the department of Commercial Taxes.
The final determination was made on May 3, 1960, and by that determination, the Post of a Sales Tax Officer, Class II of the former State of Hyderabad and that of a Sales - tax Officer, Grade III of the then State of Bombay were equated, with effect from November 1, 1956, with that of an Assistant Commercial Tax Officer in the new State of Mysore. The petitioners contend that by this classification which, according to them, the State had no competence to make, and which transgressed the proviso appearing under S.115(7) of the State Re - organisation Act, they were reduced in rank in violation of Art.311(2) of the Constitution.

3. Until October, 1957, four sales - tax laws were operating in the new State of Mysore. They were the Mysore Sales - tax Act, 1948 the Hyderabad General Sales - tax Act, the Bombay Sales - tax Act and the Madras General Sales Tax Act. The assessing authorities having power to make assessments of sales tax under those laws were : -
(1) Under the Mysore Sales Tax Act, 1948,
(a) Sales Tax Officers, and
(b) Assistant Sales Tax Officers;
(2) under the Hyderabad General Sales Tax Act,
(a) Sales Tax Officers, Class I,
(b) Sales Tax Officers, Class II, and,
(c) Assistant Sales Tax Officers;
(3) under the Bombay Sales Tax Act,
(a) Sales Tax Officers, Grade II, and,
(b) Sales Tax Officers, Grade III; and
(4) under the Madras General Sales Tax Act,
(a) Deputy Commercial Tax Officers and,
(b) Assistant Commercial Tax Officers.

4. It is admitted that the two classes of posts of a Sales Tax Officer in the Hyderabad State and the two grades of posts in Bombay State were in each case interchangeable in the sense that it was possible to post a Sales Tax Officer from one class or grade to another.

5. But, a notification issued in the year 1954, by the then Rajpramukh of the erstwhile Hyderabad State described a Sales Tax Officer, Class I, as a Senior Sales Tax Officer, and a Sales Tax Officer, Class II, as a Sales Tax Officer simpliciter.

6. In the former State of Mysore, there was only one class of Sales Tax Officers.

7. It was in this situation that the Mysore Sales Tax Act, 1957, (Mysore Act XXV of 1957) was enacted by the Legislature of the new State of Mysore, and it came into force on October 1, 1957. This law, which was extended to the entire new State of Mysore, repealed all the four earlier enactments, which were till then in force. The assessing authorities functioning under this new Act are the Commercial Tax Officers and the Assistant Commercial Tax Officers.

8. The enactment of this law necessitated a re - classification of the then existing assessing authorities, under the repealed laws, and the appointment under S.3 of its provisions, of Commercial Tax Officers and Assistant Commercial Tax Officers, for the performance of the functions assigned to them by the Act.

9. A notification promulgated for that purpose by the Governor of th