'Sarah's Law' gives parents in Northern Ireland power to find out if other adults are predators
Parents can be told from today if someone has a criminal record for violent or sexual offences which could put their children at risk.
The Child Protection Disclosure Scheme is a Northern Ireland version of Sarah's Law.
It allows anyone with concerns about an individual to find out if they have a history of violence or sex crime.
The scheme is similar to legislation introduced in England and Wales following the murder of Sarah Payne.
The eight-year-old was killed by convicted paedophile Roy Whiting in 2000.
Information can be disclosed on individuals with convictions for sex crimes and relevant violent offences.
However, it will only be provided to a child's parents or guardians.
DUP MLA Lord Morrow, who campaigned to introduce the legislation, said it was vital that children were protected.
"My concerns lie with the victims and potential victims who likewise are entitled to live free from risk of predators," he told the Belfast Telegraph.
"If offenders, both sexual and violent, are to be managed in the community, then the community must be adequately protected."
The Belfast Telegraph reported that Sarah's Law-style legislation would be introduced to Northern Ireland last March.
Sarah's Law, known formally as the Child Sex Offender Disclosure Scheme, was introduced in England and Wales following a long campaign by Sara Payne, the schoolgirl's mother.
The Northern Ireland legislation goes beyond this, and allows for disclosure of violent crime which could cause a risk to children.
It was tabled by Lord Morrow and party colleague Paul Frew, and forms part of the 2015 Justice Act.
Detective Chief Superintendent George Clarke, head of the PSNI's public protection branch, said police were committed to keeping children safe.
"This scheme, which is in addition to the arrangements already in place, will afford members of the public with genuine concerns about the safety of a child or children the opportunity to raise those concerns with us," he said.
Disclosure of information will be carefully managed. People can make an application, identifying both the child and the individual they have concerns about.
Police will have up to 28 days to assess the application.
The information about an individual will not necessarily be released to the applicant. It will be given to the person responsible for the child, and only if considered necessary.
Fears had previously been expressed that the scheme could drive child sex offenders underground, or cause vigilante-style attacks.
However, Supt Clarke added: "When a disclosure is made, it's made to an identified person and that identified person acknowledges when the disclosure is made that they have responsibilities about how they use that information.
"I would really hope that people who are making applications to safeguard children aren't doing it for a reason other than that."
Sex offenders have been targets for paramilitary gangs in the past. Supt Clarke added: "The scourge of paramilitarism is something that is a reality.
"If people want to hijack the abuse of children as some sort of flag of convenience for other criminality they want to embark on, that's a sad feature of life here. The reality is this scheme has been thought through in a way that actually discloses conviction information to people who have responsibility to protect a child."
Colin Reid, of NSPCC Northern Ireland, warned: "While the new measures are important, people should not rely solely on a system of disclosure to protect children, as the risk of sexual harm can come from persons known to the child but not known to the police."