Doctrine of Severability :

One thing to be noted in Article 13 is that, it is not the entire law which is affected by the provisions in Part III, but on the other hand, the law becomes invalid only to the extent to which it is inconsistent with the Fundamental Rights. So only that part of the law will be declared invalid which is inconsistent, and the rest of the law will stand. However, on this point a clarification has been made by the Courts that invalid part of the law shall be severed and declared invalid if really it is severable, i.e., if after separating the invalid part the valid part is capable of giving effect to the legislature’s intent, then only it will survive, otherwise the Court shall declare the entire law as invalid. This is known as the rule of severability.

The doctrine has been applied invariably to cases where it has been found possible to separate the invalid part from the valid part of an Act. Article 13 only says that any law which is inconsistent with the fundamental rights is void “to the extent of inconsistency” and this has been interpreted to imply that it is not necessary to strike down the whole Act as invalid, if only a part is invalid and that part can survive independently. In A.K. Gopalan v. State of Madras, A.I.R.1950 S.C. 27, the Supreme Court ruled that where an Act was partly invalid, if the valid portion was severable from the rest, the valid portion would be maintained, provided that it was sufficient to carry out the purpose of the Act.

From above, it is clear that this doctrine applies only to pre constitutional laws as according to Article 13(2), State cannot even make any law which is contrary to the provisions of this Part.