The Parole Board says it will not be requesting changes to the laws covering the release of high-risk offenders from jail.
Justice Minister Simon Power says he would consider law changes to make it easier to keep such offenders in prison if they are requested by the Parole Board.
The board says it has no option but to release Benny Haerewa in December despite holding grave fears that he will reoffend quickly.
Haerewa beat four-year-old James Whakaruru to death in April 1999 and his sentence for manslaughter is almost up.
Justice lobby groups are calling for preventive detention to be more widely available.
But the Parole Board on Wednesday said Haerewa was sentenced under old laws and the problems were fixed when they were changed in 2002.
The director of the group Rethinking Crime and Punishment, Kim Workman, says it is another example of why preventive sentences need to be available to judges in murder and manslaughter cases.
The Sensible Sentencing Trust is calling on the Government to change the law retrospectively so Haerewa can be held in prison.
However, a former president of the Criminal Bar Association, Graeme Newell, says preventive detention has to be given at the time of the sentence, and not by the Parole Board at release time, because that would mean punishing an offender twice.
The convenor of the Criminal Committee of the Law Society, Jonathan Krebs, says parole laws should not be changed on the basis of a few high-profile cases.
He says the law already allows preventive detention to keep an offender in prison, and that sentence should be used more frequently.
Grave fears still held
Haerewa must be freed on 20 December because he will have almost served his full 12-year manslaughter sentence.
The Parole Board says, however, that he is likely to reoffend and that it still has grave fears about his risk to the community as a serious violent offender.
It acknowledges that James Whakaruru's family is troubled by the decision but says it is inevitable.
Eleven conditions have been attached to Haerewa's release. He must undertake drug, alcohol and psychological assessments and keep away from gangs and those 16 and under.
Trust calls for law change
The Sensible Sentencing Trust says a law change is needed to prevent offenders like Haerewa from being released when they are still a risk to the community.
"I don't think many New Zealanders would be up in arms," says trust spokesperson Garth McVicar, "if we passed retrospective legislation tomorrow that gave Parliament the right to put a preventive-detention sentence on him now, so the safety of the citizens came before his rights."
Justice Minister Simon Power says he does not comment on Parole Board decisions but says that if the board has suggested there are problems with the law he is willing to review it. A retrospective law change to deny Haerewa release is probably not the answer, he says.
The Children's Commissioner at the time of the trial, Roger McClay, says the release of a child's killer from jail should be an opportunity to reflect on what went wrong, and to find solutions to child abuse.
He suggests implementing the mandatory reporting of child abuse, which he says could have saved James Whakaruru's life.
Limit to monitoring
The Probation Service says there is a limit on how long it can monitor a high-risk offender being released from prison soon.
The service's general manager, Katrina Casey, told Nine to Noon that probation officers will follow Haerewa closely for six months in case he breaches any release condition.
Mr Workman says it is anyone's guess what will happen after that.
Ms Casey says the offender was sentenced under an old law, so there is only a very small window in which he can be recalled to prison.