A lawyer who represented some of the people originally accused of taking part military-style training camps in Te Urewera National Park says the case should never have gone ahead.
A jury in the Auckland High Court on Tuesday was unable to agree on whether Tame Iti, Te Rangikaiwhiria Kemara, Urs Signer and Emily Bailey were part of an organised criminal group.
They were convicted of the illegal possession of firearms and restricted weapons, namely a Molotov cocktail, in Te Urewera National Park and have been remanded on bail for sentencing on 24 May this year.
The Crown had alleged that the four wanted to create a revolutionary army willing to kidnap and murder to get self-governance for the Tuhoe people.
Annette Sykes is one of the lawyers who successfully argued that covert video footage vital to the prosecution was collected illegally.
Consequently, charges against 14 of the original accused were dropped, but the case against Iti, Kemara, Signer and Bailey proceeded.
Ms Sykes says they should not have had any of the evidence used against them.
"You've got 14 people who were not able to be proceeded with on the same charges, because the evidence was tainted, walking free while you've got four who were singled out on a single charge that is unable to be proved now being sentenced.
"It's a huge novelty and it may be an anomaly that may need to be tested once the sentencing outcome is known."
Before sentencing, the Crown will have to decide if it wants to retry the group on the criminal group charge.
A public and criminal law expert, Grant Illingworth, says the matter of public interest will be a consideration.
A decision on a retrial is expected to be made by April.