All North Indian languages are derived from Proto European languages. Sure, Hindi has the sway in a large part of the country, but it is a language that is based on Sanskrit which was based on the language spoken by Central Asian people or Aryans (depending on which theory you believe) who came and settled in India. English is spoken in India because of the English invasion. But English is also an official language and we have made it our own. Even the formal English that we use is peppered with Indianisms. I dare you to find the word 'prepone' in the King's English. So rather than seeing this as a relic of Britain, I think we are now colonizing English. It gives us advantages in making us more employable, allowing global trade more easily and in making us more attractive for investments from across the world. It is our soft power and I see no good reason to give up soft power for linguistic chauvinism. If we want to be truly Indian, why not speak Tamil since it is India's oldest language and the ancestors of Tamil speakers were possibly the original inhabitants of India? I have no bias towards them because I am somewhat North-ish but logic would demand that.

As for the law, having laws in English makes it easier for practitioners from across the country to practice the law. Why would you want to add a stumbling block to people from one region to practice the law that is applicable to all?