Special Provisions
(1) Until Parliament legislates otherwise: Supreme Court and High Court proceedings, and the authoritative texts of Bills/Acts/Ordinances/orders/rules/regulations/bye-laws, are in English. (2) A Governor may, with the President's prior consent, authorise Hindi or another state official language in proceedings of that state's principal High Court (but not for the actual judgment/decree/order itself, which stays in English). (3) If a state uses a non-English language for its Bills/Acts/Ordinances/rules, an English translation published in the state's Official Gazette becomes the authoritative English text.
This keeps the highest levels of India's legal system - the Supreme Court, High Courts, and the authoritative text of all laws - anchored in English by default, even though a state can get permission to conduct some High Court proceedings in Hindi or a regional language, with the crucial exception that the actual final judgment must still be rendered in English.
This is why, even where a High Court permits arguments to be made in Hindi or a regional language, the actual written judgment itself is still issued in English - a specific carve-out this article maintains regardless of what proceedings language is otherwise authorised.