Foreign Minister Julie Bishop has refused to explain why documents about Australian spy operations during the Indonesian occupation of East Timor should remain secret.
Since 2014, Canberra academic Clinton Fernandes has been trying to get access to the Australian Secret Intelligence Service's 43-year old records about East Timor through the National Archives of Australia.
The overseas secret intelligence director general Paul Symon was due to argue against release at an Administrative Appeals Tribunal private hearing on Friday.
"It is not the practice of the Australian government to comment on intelligence matters," Ms Bishop told reporters in Sydney. She said the matter was before the tribunal and it would be inappropriate for her to provide a running commentary.
Professor Fernandes said his legal team hopes in the proceedings to ask questions that make ASIS justify why on national security grounds the materials should continue to be withheld 43 years after the event.
"It was common knowledge that Australia was involved in East Timor and was very interested in Indonesia in the 1970s," the University of New South Wales professor told the ABC.
He believes the documents could shed light on events leading up to the 1975 deaths of five Australian journalists at Balibo.