What else would it would it replace?
Your Jharkhand Law Council clearly has a different opinion.
Here is a commentary by
Amitesh Lal, Principal Judge, Family Courts, Jamshedpur
Let me know what you think of his opinion.
The principal law governing marriage in India
is the Hindu Marriage Act, 1955 and The Special Marriage Act,
1954. The Hindu Marriage Act applies to all Hindus, including
Sikhs, Buddhists and Jains but not to persons of tribal
community. This is because the Act was designed to apply to
Hindus, and tribals are not considered to be Hindus under the
Act. For tribal communities, the laws are even more complex,
as they are often based on traditional customs and practices
that may not be in line with the laws of the land and till date
remain uncodified. The tribes have their own traditional laws
governing marriage, which are based on their own customs
and practices. The Special Marriage Act, 1954, provides a
secular alternative to Hindu marriage, and can be used by
any Indian citizen, regardless of religion.