Jallikattu, which sees young men wrestling with a bull in an open field during the harvest festival of Pongal, was banned by the Supreme Court in 2014.
Animal rights activists say bulls are abused, tortured, taunted with chillis flung in their eyes, and are doped on liquor.
Lakhs in Tamil Nadu say that's not correct and that those who oppose Jallikattu do not understand the region's culture or respect it.
Last year, the centre allowed the sport, but that decision has been challenged in the Supreme Court, which today agreed that it would not rule on the matter for a week.
Pongal was held last week. Hundreds of people who defied the ban to hold local competitions in parts of Tamil Nadu were arrested, triggering a massive backlash.
Students took the lead in rallying people across the state. In Chennai, on the shoreline, they gathered in thousands, their numbers growing everyday with the extensive use of social media.
Students have ensured that the protests remain apolitical and peaceful. Many of the demonstrators have helped clean up litter along the beach. Politicians who tried to join the mass demonstration were asked to leave.
Tamil Nadu has used an executive order to clear Jallikattu - with some new restrictions - under a law that prevents cruelty to animals. States and centre both have legislative powers on this matter.
Prime Minister Narendra Modi met Tamil Nadu Chief Minister O Panneerselvam yesterday, and indicated that though the centre cannot intervene while the Supreme Court is deciding on ending the ban, his government will support measures taken by the state.
Once the executive order is approved by President Mukherjee, it will be cleared by the Governor of Tamil Nadu, most likely no later than Sunday.
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