The Rajasthan High Court had equated the Jain ritual of 'Santhara' with suicide.
Thousands of Jains protested across India on Monday for the legal right to take part in an ancient ritual of starving themselves to death.
Dressed in white kurta-pyjamas, holding banners that read "Suicide is crime. Santhara is religion," they marched silently through Jaipur in Rajasthan, where the High Court ruled this month that their voluntary custom of fasting until death or Santhara is a form of suicide, and therefore illegal.
"Our peaceful protest is against the judgement pronounced by the High Court without understanding the concept and objectives" of the tradition, Jain leader Rajendra Godha said.
The protest that snaked through Jaipur for several kilometres saw schools and businesses run by Jains close for the day.
Smaller protests were also held in other cities including in Mumbai, where several thousand gathered peacefully under a tent to hear speeches by two priests.
Jain leaders have said they will appeal to the Supreme Court against the High Court's ruling, saying the decision was against their religious right which is enshrined in the Constitution.
As part of their religion, Jains can take a vow to give up food and water as a way of embracing death. It is unclear how many deaths occur every year but local media put the number at a couple of hundred.
The High Court verdict was based on a petition by an activist in Rajasthan who argued the practice was against the law. He questioned whether elderly Jains were being encouraged to take the vow to free families of the burden of taking care of them, an argument Jains deny.