Photo: AFP PHOTO / HO / USAR
Police decided in 2017 not to lay 115 charges of manslaughter against the building's designer David Harding, and his employer Alan Reay.
The decision followed advice from the Solicitor General that a prosecution would not succeed.
Last year, the families complained to the IPCA.
In September this year, the authority said it had no jurisdiction over decisions made by Crown Law.
Maan Alkaisi
Photo: RNZ / Richard Tindiller
Families spokesperson Maan Alkaisi said despite this, the battle for justice would continue.
"We have never seen a worse design than this building, there's definitely a major departure [from the expected standard]. Even the IPCA admitted that there are numerous design deficiencies and a major departure."