But Mrs Collins said ex-prisoners who were still under the strictest supervision orders when the bill passed could be subject to an order.
This meant notorious sex offender Stewart Murray Wilson could be eligible for a public protection order because his strict supervision conditions lasted for 10 years.
He was released last month under 24-hour-a-day supervision in Wanganui despite a high risk of reoffending.
Mrs Collins said the test for handing down an order would be very high, and prisoners could ask for a review of the High Court's decision.
Some offenders who have been given an order would live in separate residences within prison grounds, and have more civil rights than other prisoners such as the ability to vote in elections or referendums.
Labour Party justice spokesman Charles Chauvel said he would recommend his party vote for the bill at the first reading because it was an important issue. But he slammed National's slow progress with it after the party described it as urgent at election time.
"In the interim, one of the five to 12 offenders it specifically targets - Stewart Murray Wilson - has already been released," Mr Chauvel said.
Rethinking Crime and Punishment spokesman Kim Workman said he believed the bill was designed to capture a handful of sex offenders who had been sentenced shortly before preventive detention was introduced.
After these people were picked up by the new system, the law could be repealed, he said.
A regulatory impact statement prepared by the Corrections Department said the new bill could be controversial in New Zealand and internationally because it was likely to breach human rights obligations.
Attorney-General Chris Finlayson has reviewed the legislation and has not found reason to attach a section 7 notice - an indication to the House that a law breached the Bill of Rights.
This meant the new law might still have some inconsistencies with the Bill of Rights, but these inconsistencies have been considered "justifiable".
In a review of extended supervision orders law in 2009, Mr Finlayson expressed concern about ordering a person's detention as a precaution against future offending.
Playing it safe
Now
* Offenders sentenced before the introduction of preventive detention must be released at the end of their finite jail term, even if they are at a high risk of reoffending.
* They can be placed on a highly restrictive extended supervision order.
Proposed
* Authorities can apply for public protection orders for a sexual or violent offender as they approach release from jail, or if they have been released on an extended supervision order.
* The orders will be decided by the High Court, and an offender can ask for a review of the decision.
