Answer:
While the right to privacy isn't specifically mentioned in the Constitution, the US Supreme Court decided privacy is an implied right under the 14th Amendment Due Process Clause.
The judicial concept is called "Substantive Due Process," which holds that the Fourteenth Amendment Due Process Clause is intended to protect all unenumerated rights considered fundamental and "implicit in the concept of ordered liberty," among these the right to privacy. Use of Substantive Due Process is considered judicial activism, in that it seeks to limit the scope of laws that undermine personal liberty, even if the law doesn't address a right specifically mentioned in the Constitution.