What happened
Justice K. S. Puttaswamy, a retired judge of the Karnataka High Court, and another petitioner filed Writ Petition (Civil) No. 494 of 2012 challenging the Aadhaar scheme. The challenge was made primarily on the ground that the scheme violated the fundamental rights of citizens, and in particular the right to privacy under Article 21. In answer, the Union government raised a threshold objection of considerable force: there is no fundamental right to privacy in the Indian Constitution at all. That argument was not fanciful. It rested on two decisions of the Supreme Court's own larger benches — M. P. Sharma v. Satish Chandra, decided by eight judges in 1954, and Kharak Singh v. State of Uttar Pradesh, decided by six judges in 1962 — which had been read as holding that the Constitution contains no guaranteed right of privacy. Because those decisions came from benches of eight and six judges, no smaller bench could depart from them. The question therefore had to be settled by a bench of nine. That bench was constituted to answer one preliminary question before the Aadhaar challenge itself could proceed: whether privacy is a fundamental right protected by the Constitution. It delivered its answer on 24 August 2017.
What the court held
The nine judges held unanimously that the right to privacy is a fundamental right. They located it in Article 21 as intrinsic to the guarantee of life and personal liberty, and as also arising from the other freedoms guaranteed by Part III — it is traceable to Articles 14, 19 and 21 read together, rather than sitting in any single clause. Several separate opinions were written, but on the central question there was no dissent. To reach that conclusion the Court had to clear away its own precedent, and it did so expressly: M. P. Sharma and Kharak Singh were overruled to the extent that they held there is no constitutionally protected right of privacy. The Court also rejected the older approach, associated with the Gopalan line of cases, which treated the fundamental rights as isolated compartments — an approach already substantially displaced by Maneka Gandhi. The Court was equally clear that the right is not absolute. Privacy can be restricted, but any intrusion by the State must satisfy a demanding standard: there must be a law authorising it, the restriction must serve a legitimate state aim or compelling state interest, and the means adopted must be proportionate to that aim. That framework — legality, legitimate aim, proportionality — is what later challenges to surveillance, data collection and identification systems are tested against.
The law behind it
The right is located principally in Article 21 — no person shall be deprived of life or personal liberty except according to procedure established by law — read together with Article 14 (equality and the guarantee against arbitrariness) and Article 19 (the freedoms). Privacy is not mentioned anywhere in the text of the Constitution; the Court held that it does not need to be, because it is intrinsic to the rights that are expressly guaranteed.
The two decisions overruled were M. P. Sharma v. Satish Chandra (1954), an eight-judge decision concerning search and seizure, and Kharak Singh v. State of Uttar Pradesh (1962), a six-judge decision concerning police surveillance of a suspect's home. Because a bench cannot overrule a larger one, correcting them required nine judges — which is the whole reason this bench existed.
The proportionality standard the Court articulated is the practical heart of the judgment: a restriction on privacy must be backed by law, must pursue a legitimate aim, and the extent of the intrusion must be proportionate to the object it serves.
This judgment is the constitutional foundation on which India's data protection framework, the Digital Personal Data Protection Act, 2023, was built. Our legal knowledge centre explains these provisions in plain language, and you can ask our AI assistant about how they apply to you.
What it changed
Puttaswamy is among the most consequential Indian judgments of this century. It supplied the constitutional basis on which the Aadhaar scheme itself was later examined, and it has been relied on in challenges concerning surveillance, criminal law and personal autonomy — including the decisions decriminalising consensual same-sex relations and striking down the offence of adultery. It is the doctrinal foundation of India's Digital Personal Data Protection Act, 2023. Its second legacy is methodological: the legality–legitimate aim–proportionality test it set out is now the standard framework Indian courts apply when a fundamental right is restricted.
What this means for you
Privacy being a fundamental right changes what the State has to justify. It cannot collect, retain or share your personal information simply because it finds it convenient. If a government measure intrudes on your privacy — surveillance, mandatory collection of biometric or personal data, disclosure of your information to a third party — it must be backed by an actual law, must serve a legitimate aim, and must be proportionate. That is a test that measures can and do fail. Practically, this is the judgment behind your rights over your own data: the reason you have a say in how your personal information is collected and used, the reason a data protection statute exists, and the reason challenges to intrusive state measures have a constitutional hook to hang on. It also protects a broader zone of personal autonomy — decisions about your body, your relationships, your beliefs and your home — which the Court treated as part of what privacy means, not merely secrecy of information. Note the limit as well: the right runs primarily against the State, and a private dispute about someone sharing your information will usually be pursued under data protection law, criminal law or civil remedies rather than by writ petition.
Source
Supreme Court of India, A nine-judge bench headed by Chief Justice J. S. Khehar, including Justices J. Chelameswar, S. A. Bobde, R. K. Agrawal, R. F. Nariman, A. M. Sapre, D. Y. Chandrachud, S. K. Kaul and S. A. Nazeer, 24 August 2017. Citation: AIR 2017 SC 4161; (2017) 10 SCC 1. Read the full judgment .
This explainer was written from the primary judgment text, not from news reports.