The doctrine of severability has been elaborately considered by the Supreme Court in R.M.D.C. v. Union of India, AIR 1957 S.C. 628 and the following rules regarding the question of severability has been laid down :
(1) The intention of the legislature is the determining factor in determining whether the valid parts of a statute are severable from the invalid parts.
(2) If the valid and invalid provisions are so inextricably mixed up that they cannot be separated from another, then the invalidity of a portion must result in the invalidity of the Act in its entirety. On the other hand, if they are so distinct and separate that after striking out what is invalid what remains is itself a complete code independent of the rest, then it will be upheld notwithstanding that the rest had become unenforceable.
(3) Even when the provisions which are valid, are distinct and separate from those which are invalid if they form part of a single scheme which is intended to be operative as a whole, then also the Invalidity of a part will result in the failure of the whole.
(4) Likewise, when the valid and invalid parts of a statute are independent and do not form part of a scheme but what is left after omitting the invalid portion is so thin and truncated as to be in substance different from what it was when it emerged out of the legislature, then also it will be rejected in its entirety.
(5) The severability of the valid and invalid provisions of a statute does not depend on whether provisions are enacted in the same section or different section, it is not the form but the substance of the matter that is material, and that has to be ascertained on an examination of the Act as a whole and of the setting of the relevant provisions therein.
(6) If after the invalid portion is expunged from the statute what remains cannot be enforced without making alterations and modifications therein, then the whole of it must be struck down as void, as otherwise it will amount to judicial legislation.
(7) In determining the legislative intent on the question of severability, it will be legitimate to take into account the history of the legislation, its objects, the title and the preamble to it.
In R.M.D.C. v. Union of India, the validity of Section 2 (d) of the Prize Competitions Act, which was broad enough to include competitions of a gambling nature as well as competitions involved? The Supreme Court held that the provisions of the Act were valid in so far as they were severable and hence struck down only those provisions which related to competitions involving skill.
The Court held in this case that valid provisions of the Act were severable and they constituted a complete code in itself. So there was no necessity to declare the whole Act as invalid. The test here was that whether the legislature would have enacted the valid part if it had known that the rest of the statute was invalid.
In Stale of Bombay v. F.N. Balsara, AIR 1951 S.C. 318, it was held that the provisions of the Bombay Prohibition Act, 1949 which were declared as void, did not affect the validity of the entire Act and therefore there was no necessity for declaring the entire statute as invalid. Hence, the doctrine of severability was applied therein.
This doctrine of severability was also applied in D.S. Nakara v. Union of India, AIR 1983 S.C. 130, where the Act remained valid while the invalid portion of it, was declared invalid because it was severable from the rest of the Act. The severable invalid provisions could be struck down not only to restrict but to enlarge the application of law if such enlargement would save the Act.