Maneesh,
Registration of ALL marriages is compulsory in India.
The Supreme Court had a made a ruling in this regard in February 2006.
http://timesofindia.indiatimes.com/I...70,curpg-1.cms
There was some confusion about the applicability of this to non-Hindu marriages.
But, this was also clarified by the Supreme Court, this week:
Register all marriages, says SC- Hindustan Times