Abul Rizvi said the tennis superstar had "every legal right to think" he could contest this month's Australian Open after initially being granted a visa to enter Australia, after being given the all clear from Tennis Australia and the Victorian government to participate in the event.

The former Immigration Department deputy secretary made the comments on Friday as Home Affairs Minister Karen Andrews confirmed Border Force was now investigating potential visa issues with two other Australian Open participants.

The world No.1 will remain locked in immigration detention in Melbourne until at least Monday, when his legal fight to overturn the government's last-minute decision to cancel his visa returns to court.

Immigration law experts who spoke to The Canberra Times believed Djokovic's visa was cancelled under section 116 of the Migration Act, which allows the minister to cancel the visa of a person who might pose a risk to public health and safety.

Anyone whose visa is cancelled can be banned from re-entering Australia for up to three years.

The visa decision, which has sparked outrage in Djokovic's home country of Serbia and created another diplomatic headache for the Morrison government, was made on the grounds Djokovic had failed to provide "appropriate evidence" of an exemption to enter Australia unvaccinated.

Prime Minister Scott Morrison declared "rules are rules and there are no special cases" as he pushed back against criticism of the decision - including from the Serbian president.

Labor treasury spokesman Jim Chalmers on Friday accused Mr Morrison of "chest-beating" on Djokovic's visa cancellation to distract the public from problems surrounding rapid home COVID tests.

Mr Rizvi told The Canberra Times the situation "should not have come to this".

He said given Djokovic's well-known anti-vaccine stance, Australian authorities should have asked for proof of his vaccination status or details of a medical exemption before the visa was issued.

Mr Rizvi noted the visa was approved despite the Commonwealth's warnings a recent COVID-19 infection - believed to be the grounds for Djokovic's application for a medical exemption - would not satisfy its border entry rules.

The Commonwealth's warnings were included in two letters sent to Tennis Australia boss Craig Tiley last November, which were released to the media just hours after Djokovic's visa was cancelled.

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The tennis star was granted a separate exemption by Tennis Australia and the Victorian government to compete in the tournament, following a process conducted by two independent expert panels.

Mr Rizvi said Djokovic's advisors would have believed the Commonwealth-issued visa and approved tournament exemption would be enough to secure entry to Australia.

"Put those two together and any reasonable person would come to the conclusion that he could come to Australia," he said.

"Despite all the warnings that he'd been given and I don't deny those, and I have no sympathy for his anti-vax views, [but] he had every legal right to think he could enter Australia and play in the Aussie Open."

Mr Rizvi said Australian officials could have warned Djokovic not to board the plane to Melbourne, but were presumably not instructed to do so.

He said the federal government would have to overhaul how it managed the visa processing of unvaccinated travellers to avoid chaos at Australian airports.

Asked to comment on how the handling of the saga reflected on the federal government, Mr Rizvi said: "It makes me incredibly sad.

"Twenty years ago, we were regarded as world class in terms of our visa system. We were as good as anybody in the world and people copied us in what we did. Now we're a laughing stock and it's very sad."

Ms Andrews earlier on Friday again defended the federal government's handling of the case.

"Ultimately every traveller has a responsibility to ensure that they are meeting requirements of entry to this country, and potentially any country around the world," she said.

In a further twist to a saga which has completely overshadowed the Australian Open build-up, acting Victorian premier Jacinta Allan revealed her government had not seen the advice the Commonwealth sent to Tennis Australia regarding rules for unvaccinated players.

Ms Allan argued it wasn't unusual for the Victorian government to be kept out of the loop given that the Commonwealth controlled who entered the country.

She reiterated the exemption process run by Tennis Australia and her government was for permission to compete in the tournament, not to enter the country.