The ACT Civil and Administrative Tribunal found in favour of Alec Wickerson and his partner Tara Williams in a decision published Tuesday, saying the Cypress met three criteria under the law for being cut down.

In its decision, the tribunal also rebuked the Conservator of Fauna and Flora, saying that its staff had failed to disclose a conflict of interest and had also allowed an "independent" decision review process to be compromised.

Neither practice should be repeated, the tribunal said.

The conservator Ian Walker told the Canberra Times in a statement on Wednesday that he would address and investigate the issues raised by the tribunal.

Although happy with the tribunal decision, Ms Williams and Mr Wickerson have been left fuming after a seventh-month process in which the right outcome had been "plainly obvious to everyone except the Tree Protection Unit".

They called for a review of the unit and the processes of having a tree removed, including heightened transparency, saying they did not want other people to go through what they did.

The offending tree is a 17-metre-tall Cupressus glabra, commonly known as an Arizona Cypress, a regulated tree under Canberra's tree protection laws.

Mr Wickerson applied to remove the tree on September 6, 2017, because its branches had been falling off.

Firefighters said the tree was "dangerous", the tribunal heard, while Mr Wickerson also worried about asbestos fibres in the air if a fallen branch damaged their asbestos sheeted roof.

But the Conservator of Flora and Fauna refused his request, saying the tree met no criteria that would allow the couple to remove it. After a review backed the first decision to refuse his application, Mr Wickerson took the fight to the tribunal.

In the decision published Tuesday, presidential member Elizabeth Symons found the cypress met three of the criteria that would allow the couple to have it removed.

She said the tree posed an unacceptable risk to people's safety, as well as a threat to structures, including the couple’s asbestos sheeted roof, and that the location of tree was inappropriate given its potential for size and growth.

Ms Symons also noted, with concern, how the officer who refused the couple's original tree removal application accompanied the independent advisor who came to assess the tree for a review of the original decision.

The tribunal heard that the same advisor was working for a company the couple had sought independent advice about the tree from, though that fact was not known to the couple. Ms Symons also expressed concern that the government had failed to disclose the potential conflict of interest.

She said the concerns had negatively impacted the independence and transparency of the process and that neither should happen again.

The conservator Ian Walker said that he accepted the tribunal's recommendation that he address procedures so that the original investigating officers do not attend the tree assessment for the review of an earlier decision.

He also said he would also investigate the need to "address procedures regarding how members of the Tree Advisory Panel are made aware prior to their appointment of the need to disclose potential conflicts of interest".

Speaking after the decision this week, the couple called the tree unit's processes "shonky", pointing to a lack of transparency in the decision-making and independence in the review of the original decision.

They said the unit was not properly balancing the needs of residents with the need to protect trees, and the "right outcome was so plainly obvious to all, except to those in the Tree Protection Unit, whose sole job it is to understand and apply" the law.

"What is more concerning is this was not recognised by anyone in a decision making capacity and the case went this far," the couple said, suggesting it pointed to a "systemic" attitude within the unit.