India is a country with secular polity with right to religious freedom but a highly religious society. This might be affecting laws and policies of the governments.
The stratification in and the structure of Indian society (broadly) definitely poses social challenges against atheists.
Are there any significant challenges and disadvantages of being an atheist in India in legal aspects?
The most important aspects in India which are governed by specific religious laws are:
It is easier and faster to get married using the religious laws (Hindu Marriage Act or Shariat Act), as compared to the secular marriage law (Special Marriage Act, 1954). That is why many young couples convert to a single religion to get married quickly.
So, if one decides to become the first generation atheist in a family (against the wishes of the family or the larger religious community), their inheritance and their rights (especially if they are engaged in agriculture) could be severely affected. This becomes all the more difficult, if the business of their family is not incorporated as a company under the Companies Act.
If you are professional or a first generation business owner, then you shouldn't have legal challenges but primary and secondary social challenges. Primary social challenges could be people not ready to deal with you or engage with you if you declare publicly that you are an atheist. Secondary social challenges, would be to be able to find a lawyer (in your town and whose services are affordable) who can address these challenges. And in case you go to court, the judge may not have a lot of experience or education about how to deal with atheist cases. Also, most lawyers will advise you to identify yourself as a member of a religion to avoid unnecessary legal hassle.
The main legal disadvantage is the lack of positive affirmation of the equal rights of atheists, especially in the realm of expression. There are facially neutral laws in India which prohibit "outraging" religious sentiments, for example §295a of the penal code which prohibits insults to the religion of any class of Indian citizens. While there do exist special laws (regarding family matters) that may create rights for only one religion (polygamy), the courts have agreed that the question of rights should be resolved secularly, holding in Ahmedabad St. Xaviers College v. Gujarat that
Secularism is neither anti-God nor pro-God, it treats alike the devout, the agnostic and the atheist. It eliminates God from the matters of the state and ensures that no one shall be discriminated against on the ground of religion.
The Punjab amendment to IPC 295A tests this commitment to secularity by also criminalizing "injuring, causing any damage or sacrilege to Sri Guru Granth Sahib, Srimad Bhagwad Gita, Holy Quran and Holy Bible with an intention to hurt the religious feeling of the people" (prohibiting criticism of 4 religions while not equally protecting atheism from criticism, likewise the myriad other religions not protected by the law).
