But the idea – crafted amid widespread public concern over the release of an offender who indicated he would molest children again if freed – is not likely constitutional, a spokesman for the Iowa attorney general’s office said Tuesday. One reason: Courts could deem that “preventive detention,” a concept that is illegal under state and federal law.  “We are doubtful this kind of measure can pass constitutional muster,” spokesman Bob Brammer said.

Culver’s plan, unveiled by his spokesman, Troy Price, in an e-mail to The Des Moines Register, would give state corrections officials authority to revoke parole without first releasing sex offenders – and keep them in prison for up to two more years …

The idea to revoke parole without ever having released a sex offender appears to be unprecedented across the country, according to some tracking of state laws done by the National Conference of State Legislatures … [However, m]ost states already have enhanced or expanded criminal penalties, mandatory reporting laws, restrictions controlling offenders’ movement and global-positioning technology to track their whereabouts …

Iowa is one of more than 30 states that have civil commitment facilities for sex offenders, but most of the state’s more than 6,000 registered offenders are ineligible to be sent there.   Before a person is civilly committed as a sexual predator, state law requires the state to prove beyond a reasonable doubt the person suffers from a mental abnormality that makes him likely to commit more sex crimes unless confined to a secure facility.
Legal experts say that’s a high legal burden to prove.