In Kansas v. Hendricks, the Supreme Court relied heavily on Hendricks's lack of “volitional control” to justify the use of civil commitment as a tool of social control. The Court's decision is best explained by the rule that police power commitment is constitutional only if it is a principled and narrow exception to the primacy of the criminal justice system. Despite the Court's failure to adopt a parens patriae or treatment-appropriateness limit, the Hendricks doctrine has the potential to confine civil commitment to its appropriate domain. But the Court's application of its principle is dangerously ambiguous. “Volitional incapacity” may be an empty rhetorical ploy; or, it may embody a pernicious “jurisprudence of difference,” equating mental difference with the degradation of civic personhood. If volitional incapacity identifies those who are too sick to deserve punishment, the Court's decision is on sound moral terrain.