The January 2020 fire tore through Namadgi National Park after it was ignited by a defence helicopter during a reconnaissance exercise.

The fire burnt across the territory for one month and led to the Clear Range and Calabash fires across the border that left numerous properties destroyed.

Chief Coroner Lorraine Walker in January ruled against the nine Bumbalong residents from appearing in the inquiry after they requested for one to be held.

In refusing the application, Ms Walker said the Coroners Act did not allow her to inquire about incidents outside the ACT with death-related matters excepted.

Among her reasoning, she said the NSW residents would not be called because she did not find they would bring knowledge or expertise beyond that of the general public.

The residents' lawyers filed an originating claim in the ACT Supreme Court and the matter was heard on Wednesday.

Barrister Wayne Sharwood, acting for the plaintiffs, argued against the jurisdictional physical constraints, saying the factor was "not an appropriate matter to have consideration" for.

As for whether his clients could bring evidence for consideration, Mr Sharwood said "it's hard to see why that's a proper consideration" because at the time of the decision being made, the terms of reference were not finalised.

Mr Sharwood said the two fires were one and that there may be potential for a duplicate inquiry if NSW were to hold one.

"It is accepted by everyone that the Orroral Valley Fire morphed into the Clear Range Fire," he said.

Mr Sharwood said the "central point" was that where properties were destroyed was legally irrelevant.

The court heard that the NSW Coroner's Court has ruled against holding an inquiry about the Clear Range fire because the state's police did not report it as it originated in the ACT.

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Houda Younan SC, representing the Coroner's Court, said the plaintiffs' argument that it was irrelevant to consider geographical limitation was without substantiation.

She said that the power of the coroner is limited to investigating matters within a physical jurisdiction unless extended by exception such as with deaths in which case jurisdiction is extended to the deaths of people ordinarily residents in the ACT.

"There is no such provision in relation to fires," she said.

Ms Younan said the potential for a duplicate inquiry was "not necessarily the case".

"The cause and origin of the fire in the ACT may be different from the cause and origin of the fire as manifest or the fire that morphed in NSW," she said.

She referred to another judgment that involved the "complicated discussion of causes of fires".

"[The] court observed that the permutation of the fire may be such that there are intervening causes," she said.

Ms Younan said the plaintiffs did not have a legal interest that would give "rise to a right of standing or a right to appear".

Earlier in the hearing, the ACT Government was removed from the proceedings as a second defendant.

Ms Younan, who also acted for the government, said the unopposed application to remove it was because it was inappropriately and unnecessarily included as a party.

Chief Justice Lucy McCallum, who said it was "an interesting metaphysical question" about a fire and jurisdictional or geographical delineation, has reserved her decision.

The inquiry is listed to run in July.

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