A nine-member Supreme Court bench unanimously ruled Thursday that privacy was part of the right to life and personal liberty as enshrined in the Indian Constitution. The ruling could affect the South Asian country's gigantic identity card scheme.
Government counsels had argued the constitution did not guarantee individual privacy as an inalienable fundamental right and that reasonable restrictions needed to be introduced.
The verdict is seen as a blow to India's ambitious biometric identification project, Aadhaar, whose scope Prime Minister Narendra Modi's government has pushed hard to expand.
The petitioners had challenged the validity of the Aadhaar card that assigns a unique 12-digit ID to every individual. The Aadhaar database links iris scans and fingerprints of the individuals to their personal data.
Modi's government has made the identity card mandatory for all citizens to receive welfare benefits, but critics raised concerns about the risk of personal data being misused.
"Today we can once again celebrate our freedom. Tomorrow there will be more challenges and we shall overcome them," said former finance minister and an official of the opposition Congress party, P. Chidambaram, following the Thursday ruling.
Chidambaram pointed out that Aadhaar was "inconsistent" with the right to privacy and infringed on people's lives.
"The SC [Supreme Court] decision marks a major blow to fascist forces. A sound rejection of the BJP's [ruling Bharatiya Janata Party] ideology of suppression through surveillance," Rahul Gandhi, Congress' vice president, wrote on Twitter.
But the Aadhaar project, administered by the Unique Identification Authority of India (UIDAI), was originally introduced in 2009 by the previous Congress-led government, with the intention that Indian citizens could better avail the benefits of social welfare schemes and government subsidies if everyone had a unique identity number.
Later, after Modi's BJP took power in 2014, the scheme was extended to other areas such as tax filing, school admissions, bank accounts, securing loans and employment details.
The BJP government welcomed the Supreme Court's ruling but maintained that the Aadhaar scheme had proven to be very successful.
"It [The scheme] is completely safe and secure. The system operates on the principle of minimum information, maximum use," said Law Minister Ravi Shankar Prasad.
The apex court judgment did not comment on whether the government's demand for Aadhaar to be linked to all financial transactions also amounted to an infringement on privacy.
"This order was not meant to decide on the fate of Aadhaar but just on whether privacy of an individual was a part of their inviolable fundamental rights. A separate five-judge bench of the Supreme Court will decide whether Aadhaar violates individual privacy," Arvind Datar, a lawyer, told DW.
The government will now have to convince the court that forcing citizens to give their fingerprints and a scan of their iris is not a violation of privacy.
Many countries in the world use ID systems that allocate citizens a unique number that contains personal details. But rights activists in India argue that the personal data gathered under the Aadhaar program is prone to misuse and surveillance. They also say that a centralized and interlinked database could lead to commercial abuse.
"There have been many leakages of citizens' personal data under this scheme. The data could be used by corporate entities for their own gains. The project does not guarantee security," Nikhil Dey, a rights activist, told DW.
Meghnad S., a citizen, believes the authorities could also access citizens' data on the premise of national security.
The Thursday judgment will likely have a bearing on many other issues that have been the subject of litigation, for instance the individual's right to eat, the right to drink, and the right to marry.