The answer is: A
Explanation
(A) State of Bihar v. Kameshwar Singh
Explanation
• The doctrine of Colourable Legislation means “what cannot be done directly, cannot be done indirectly.”
• It is applied when a legislature tries to do something indirectly which it has no power to do directly under the Constitution.
• The landmark case on this doctrine is State of Bihar v. Kameshwar Singh (1952), where the Supreme Court struck down certain provisions of the Bihar Land Reforms Act as unconstitutional, holding them to be a case of colourable legislation.
Other Options (for clarity)
• M. Karunanidhi v Union of India → Deals with repugnancy between State and Union laws.
• State of Karnataka v Union of India → Concerns Centre–State relations.
• Keshavan Madhava Menon v State of Bombay → Concerns retrospective application of laws and Article 13.