In the 1996 case Kansas v. Leroy Hendricks, the U.S. Supreme Court upheld a Kansas law that allowed for civil commitment of individuals who were deemed sexually violent predators due to mental abnormalities or personality disorders making them likely to engage in predatory acts of sexual violence. The respondent, Leroy Hendricks, had an extensive history of sexually molesting children and was nearing release from prison when the state invoked this new law to keep him confined. He challenged it as unconstitutional on ex post facto and double jeopardy grounds but lost at both trial court and state supreme court levels before appealing to the U.S. Supreme Court. The high court ruled 5-4 in favor of Kansas, finding that such laws served a legitimate "civil" purpose rather than being punitive (which would have triggered protections against double jeopardy). It also held that they did not violate ex post facto prohibitions because they didn't retroactively punish past conduct but instead aimed at preventing future harm based on current conditions.

In the dissenting opinion for Kansas v. Leroy Hendricks, Justice Breyer argued that the majority's decision to uphold a law allowing indefinite civil commitment of sexually violent predators was flawed. He expressed concern over the potential misuse of this power by states and believed it could lead to arbitrary or discriminatory enforcement. Additionally, he questioned whether such laws truly served a legitimate state interest in protecting public safety or were simply punitive measures disguised as civil regulations. Furthermore, he disagreed with the majority's interpretation of "mental abnormality," arguing that it was too vague and broad to justify involuntary confinement under due process principles. Finally, Justice Breyer emphasized his belief in maintaining strict constitutional safeguards against deprivation of individual liberty without clear evidence of dangerousness and mental illness.