"The Constitution does not provide an individual with the right to use drugs. Nevertheless, the Court in Robinson held that the Constitution prohibits the State from punishing an individual simply due to his status as a drug user.198 The State is only constitutionally permitted to punish individuals for an act, not their status. In Robinson, the Court gave three reasons why the California statute criminalizing drug addiction violated the Cruel and Unusual Punishment Clause: (1) the statute did not acknowledge the status/act distinction; (2) the statute criminalized an unalterable condition; and (3) the punishment for violating the statute was not proportionate to the offense.199"

Source

Lyttle, Tiffany, "Stop The Injustice: A Protest against the Unconstitutional Punishment of Pregnant Drug-Addicted Women," The New York University Journal of Legislation and Public Policy (New York, NY: New York University School of Law, Spring 2006) Volume 9, Number 2.