In Justice K.S. Puttaswamy v. Union of India (Aadhaar case, 2018), the Supreme Court upheld the constitutional validity of Aadhaar Act but struck down mandatory linking of Aadhaar with bank accounts and mobile numbers.

Aadhaar Judgment (2018): 4:1 majority upheld Aadhaar Act for: (a) Welfare schemes (to prevent leakage), (b) PAN-Aadhaar linking (to curb tax evasion), (c) IT Act compliance. Struck down: (a) Mandatory linking with bank accounts/mobile numbers (disproportionate invasion of privacy), (b) Aadhaar authentication for school admissions (violates children's privacy). Balances state interest in welfare delivery with right to privacy.