The locus standi rule to move the court was liberalized by the case of:

The traditional rule of 'locus standi'—which dictates that only a person whose rights are directly infringed can move the court—was significantly liberalized in the landmark case of S.P. Gupta v. Union of India (1981). Justice P.N. Bhagwati, a key architect of Public Interest Litigation (PIL) in India, articulated that any public-spirited citizen or social action group acting bona fide can invoke the court's jurisdiction to enforce the rights of those unable to do so due to poverty or ignorance [1]. While Hussainara Khatoon (1979) was the first major PIL, S.P. Gupta (also known as the Judges' Transfer Case) provided the comprehensive legal foundation for expanding standing to third parties. This judicial innovation aimed to democratize access to justice for marginalized sections of society. Other options like Minerva Mills and Kesavananda Bharati primarily focused on the Basic Structure doctrine rather than procedural standing [2].

Sources

1. [1] Indian Polity, M. Laxmikanth(7th ed.) > Chapter 29: Public Interest Litigation > MEANING OF PIL > p. 309
2. [2] Indian Polity, M. Laxmikanth(7th ed.) > Chapter 90: Landmark Judgements and Their Impact > MINERVA MILLS CASE (1980) > p. 629