Step 1: Understanding the Concept:
This question relates to the effect of Article 13(1) of the Constitution of India on pre-constitutional laws. Article 13(1) states that all laws in force in India immediately before the commencement of the Constitution, in so far as they are inconsistent with the provisions of Part III (Fundamental Rights), shall be void to the extent of such inconsistency.
Step 2: Detailed Explanation:
- Doctrine of Eclipse: This doctrine applies to pre-constitutional laws that are inconsistent with Fundamental Rights. It posits that such a law is not dead or void \textit{ab initio} (from the very beginning) for all purposes. Instead, it is merely 'eclipsed' or overshadowed by the Fundamental Right and remains dormant or unenforceable against citizens. If the overshadowing Fundamental Right is amended in a way that the inconsistency is removed, the pre-constitutional law becomes revived and fully operative again automatically. It remains valid for non-citizens (against whom the Fundamental Right may not be available) and for transactions that occurred before the Constitution came into force. The leading case on this is \textit{Bhikaji Narain Dhakras v. State of M.P.}
- Doctrine of Severability: Also known as the doctrine of separability, this principle is enshrined in Article 13. It states that if an offending provision of a statute can be separated from the rest of the statute without affecting the substance of the valid part, then only the offending provision will be declared void by the court, and the rest of the statute will remain valid.
The description given in the question—that the law is not a nullity but only becomes unenforceable—is the core idea of the Doctrine of Eclipse.