Green co-leader Chlöe Swarbrick says the party welcomes the ruling and will now consider its next steps.
"As we have just received today's judgment, we will take the appropriate time to take advice and consider next steps. We will have more to say in due course."
Tana resigned from the party in March this year after an inquiry into migrant exploitation, but wants to remain in Parliament as an independent MP.
The investigation found that Tana "likely" knew about allegations of worker exploitation at her husband's business and did not disclose them to the Greens.
The hearing for a judicial review of Swarbrick, party co-leader Marama Davidson and the Greens took place at the High Court at Auckland on Thursday last week.
Justice Johnstone released the decision today.
Tana argued the investigation into allegations of worker exploration was unlawful, unauthorised by the party's constitution, unreasonable and unfair.
She also claimed she had been "ousted" from the party.
She asked the court to find that the inquiry was flawed in the ways she described.
As to whether the inquiry was unlawful, the judge said this aspect of Tana's case was "misconceived."
In regards to whether the inquiry was unauthorised, according to the Green Party's constitution, the court found the decision by Tana and the Parliamentary Caucus to commission an independent investigation was "constitutionally authorised".
Tana claimed the inquiry was "unreasonable and unfair" but Justice Johnstone did not accept this.
"The inquiry was neither unreasonable nor unfair, and certainly not in the administrative law sense that might justify declarations by way of judicial review."
In regards to the claim of being ousted from the party, the judge found Tana was "not pressured to resign as a party member".
Justice Johnstone acknowledged that Tana likely felt pressure related to her position as an MP, but said that Tana could not have been ousted as a party member.
The judge also ruled the Green Party was entitled to costs related to the case.
Tana has been contacted for comment.
