In a unanimous decision that gives new vigor to India’s Constitution and challenges the government’s rising authoritarianism, India’s Supreme Court last week affirmed the fundamental right to privacy. At the outset of an eloquent 547-page verdict, the court laid out the sweeping implications of the question before it: “If privacy is to be construed as a protected constitutional value, it would redefine in significant ways our concepts of liberty and the entitlements that flow out of its protection.”

The court’s decision was the culmination of legal challenges to India’s biometric identification program. Known as Aadhaar, the program was conceived to give India’s poor — who too often lack identification — a way to gain access to government services. But under the government of Prime Minister Narendra Modi, the scope of Aadhaar has grown alarmingly. It’s now the world’s largest biometric database, with more than a billion Indians enrolled. Initially voluntary, Aadhaar has become mandatory for such essential things as paying income taxes and opening a bank account, with government plans to expand its use. The ruling could affect the implementation of the program.

Critics of Aadhaar pointed to the growing threats to privacy from a mushrooming database that is vulnerable to security breaches and is easily exploited for government surveillance or to punish dissenters. Mr. Modi’s government argued that privacy was not a fundamental right and that security and anticorruption concerns outweighed privacy.