The Ninth Amendment presents an irresistible mystery. It speaks of "other rights" retained by the people and it prohibits interpretations which "deny or disparage" those rights. The Amendment, however, tells us nothing about what these rights are or how they can be enforced. On the one hand, this makes the Ninth rather difficult to apply. On the other hand, the lack of definitional clarity also makes the Ninth Amendment something of a desideratum for those seeking expanded judicial protection of previously unrecognized individual rights. Accordingly, the Ninth Amendment has been cited in support of everything from Dial-a-Porn to freedom from second hand smoke.
Kurt T. Lash, Originalism as Jujitsu, 25 Const. Comment. 521 (2009), (review of Daniel A. Farber, Retained by the People: The "Silent" Ninth Amendment and the Constitutional Rights Americans Don't Know They Have (2007)).