Oranga Tamariki is set to see the biggest shake-up since its inception in 2017, as The Children, Young Persons, and Their Families Legislation Act comes into full force today.

Under the law, the ministry must provide a practical commitment to the Treaty of Waitangi and offer support to young adults leaving state care until their 25th birthday.

Significant changes to the Youth Justice System also take effect today, which include the introduction of 17 year olds into the youth court.

One of the most significant changes coming into force today is that Oranga Tamariki must provide a practical commitment to the Treaty of Waitangi.

It's the first time in New Zealand's history that the Treaty has been mentioned in legislation relating to children.

The inclusion means all policies and practices affecting child well-being must have the objective of reducing disparities for tamariki and rangatahi, by having regard for their whakapapa and whānaungatanga.

Oranga Tamariki is also obligated to partner with iwi and other Māori organisations and devolve its resources and responsibilities to them.

It must also provide early intervention support and assistance, so whānau can create stable and loving homes, reducing the need for child removal.

At least once a year Oranga Tamariki must publicly report on its attempts to improve outcomes for Māori and outline any steps to be taken in the immediate future.

A new set of National Care Standards has also been introduced, which explicitly state what children in care are entitled to.

Hoani Lambert, the deputy chief executive for Voices of Children at Oranga Tamariki says it covers entitlements to clothing, to bags, to books, to connections with whanau to a whole range of services that are now properly described and prescribed in regulation and supported by our legislation.

A new transitional support service also officially launches today, providing young adults leaving state care with support to stay with caregivers until the age of 21.

They can also opt to receive ongoing support from Oranga Tamariki up until their 25th birthday.

"For many young people who have been in care, some of them have had quite an unstable experience, they might have had a number of placements, and so for these young people who may not have had the parental figures that other New Zealand young people have had, providing additional support to them has been extremely important," Hoani says.

Significant changes to the Youth Justice System also take effect today, which include the introduction of 17 year olds into the youth court.

Before this, 17 year olds were tried and sentenced in the adult district court, meaning they were not eligible for services offered by youth justice such as access to the Rangatahi and Pasifika Courts, and the expertise of multi-disciplinary teams in areas such as neurodisability, family violence, mental health and substance addiction.

Principal Youth Court Judge John Walker says today is an important step forward.

"Those young people who come into conflict with the law, so they are coming from backgrounds of serious trauma, they've got a number of neuro-disabilities.

"None of this expires at a chronological age and to have an extra year for these young people to have the benefits of the multidisciplinary approach which applies in the Youth Court is in the long term interest of the community a very important thing."

The only time 17 year olds will not be tried in the youth court is if they are charged with murder, manslaughter, or a Schedule 1A offence like aggravated robbery.

Those will continue to be heard in the district or high court.

However, a new provision in the law means they can now be transferred back to the Youth Court if the charge is reduced, amended or replaced with a less serious one.

They will now also have earlier access to youth advocates, who will be able offer legal advice during intention-to-charge family group conferences.

These conferences often take place before a trial begins, and are attended by police and other agencies.

"It will allow for discussions about the nature of the charge, and whether the charging level is correct in relation to that young person," Judge Walker says.

"The young person will be able to have advice as to whether to admit the charge or not at that early stage."

Children's Commissioner Andrew Becroft says the changes were significant and desperately needed.

He says the legislation changed state care from its old ambulance at the bottom of the cliff model, to a far more proactive and supportive model.

Judge Becroft says New Zealand needs to grasp this opportunity, and ensure that it does not wither on the vine like it did in the 1990s following the release of the Puao-Te-Ata-Tu report.

That report and the legislation that followed had offered up similar hope of revolution, but Judge Becroft said that never happened.

He said it is now more important than ever that New Zealanders work to ensure that Oranga Tamariki delivers on the promises made in this legislation.

"In language which isn't often used by a Judge this is ... a prescription for a revolution in the way the state honours Treaty obligations with Māori in respect with care of children.

"Nothing short of a revolution will do."

-RNZ/Katie_Doyle