The seven Vancouver police officers who declined to be interviewed in an investigation into a fatal shooting at a local Canadian Tire have been told they must participate.

B.C.'s police watchdog filed a petition 1 ½ years ago, asking the province's top court to help out after the officers declined to be interviewed.

On Thursday, the court sided with the Independent Investigations Office, saying: "The witness officers' statutory obligation mandates that they have a public legal duty to act, in particular to co-operate fully with the petitioner (IIO)."

The court said the obligation to co-operate is an essential element of a police oversight agency, and there would be no arms-length investigations if the IIO was at the discretion of witness officers.

Its findings mean the officers must attend interviews at the direction of investigators.

The IIO is investigating what happened on Nov. 10, 2016, when police opened fire on 38-year-old Daniel Peter Rintoul.

Prior to the shooting, Rintoul allegedly stabbed a store clerk, tried to steal firearms, held a senior hostage and stabbed an officer.

The IIO was called to investigate, as it is in any police-involved incident where someone is injured or killed, and began to look at materials including audio and video evidence.

Investigators sought to speak to the officers who'd been at the scene at the time, but claim they faced pushback when trying to question those officers.

The filing submitted to the Supreme Court read, in part, "They have demanded, through their counsel or union representative, pre-interview disclosure of certain investigative file materials in the IIO's possession as a precondition of any IIO interviews.

The watchdog said it would be willing to share its evidence with police shortly before the interviews are conducted, but that it doesn't want to influence their memories of that day.

At the time, the Vancouver Police Union said it was standing by its officers, and argued they're just trying to give the most accurate accounts of the suspect's shooting as possible.

"What the IIO are proposing is that a member would show up and give an interview just from memory," union president Tom Stamatakis said in March 2017, when the IIO filed its request.

"People don't recall accurately every little detail around what they did in any incident, let alone one that unfolds very dynamically and in a very stressful matter."

He insisted police weren't being unco-operative. They're keen to do the interviews, but only under the right conditions.

In its decision, the Supreme Court said officers cannot withhold co-operation based on assertions that the proposed interview timing is inconvenient, or that the IIO interviews will not be conducted in accordance with terms they deem appropriate. 

The IIO's chief civilian director called the ruling crucial, saying it points toward the essence of independent oversight. It will also have an impact on other cases, Ron MacDonald said.

"The decision effectively strongly reaffirmed the importance of civilian oversight of policing in British Columbia," he told CTV News.

"We do have a few other files…where the similar issue has come up and they're much more recent and we all agreed we would await the decision in this matter before moving on to those."

With files from CTV Vancouver's Michele Brunoro