A common High Court for two or more states can be established by:

According to Article 231 of the Indian Constitution, the Parliament is empowered to establish a common High Court for two or more states or for two or more states and a union territory by passing a law [1]. While Article 214 originally mandated a High Court for each state, the Seventh Amendment Act of 1956 modified this framework to allow for shared judicial institutions [1][2]. This legislative power is exclusive to the Parliament, meaning neither an order from the Supreme Court nor a direct order from the President can establish such a court. Examples of such arrangements include the Bombay High Court, which serves Maharashtra and Goa, and the Punjab and Haryana High Court [3]. Currently, India has 25 High Courts, with only a few exercising jurisdiction over multiple states [1].

Sources

1. [1] Laxmikanth, M. Indian Polity. 7th ed., McGraw Hill. > Chapter 34: High Court > 34 ~ CHAPliER > p. 353
2. [2] Indian Polity, M. Laxmikanth(7th ed.) > Chapter 34: High Court > 34 ~ CHAPliER > p. 353
3. [3] Indian Polity, M. Laxmikanth(7th ed.) > Chapter 15: Centre-State Relations > 8. | Integrated Judicial System > p. 151