Australia's outright travel ban blocking its own citizens from leaving the country is unique in the free world.
Kiwis, Britons, Canadians and Americans are able to depart the country, while Australia provides only a handful of exemptions for residents to travel.
Constitutional experts say the exit ban is legally sound, but one says there is a "hook" someone could use to challenge the restriction in court.
Monash University associate professor Luke Beck says the Constitution gives the federal parliament "very broad powers" to make laws relating to external affairs.
The travel ban falls under Section 477 of the Biosecurity Act 2015 which gives the Health Minister power to make rules restricting people or things "entering or leaving specified places".
But the legislation carries an important caveat: the rules must be "no more restrictive or intrusive than is required in the circumstances".
Dr Beck said addressing this clause would be "the most obvious way" to challenge the exit ban, by arguing the blanket ban is more restrictive than necessary.
"It all comes down to what is proportionate," Dr Beck said. "Coming home from Auckland isn't the same as coming home from London [given the UK's spike in COVID-19 cases].
University of NSW law professor George Williams said while several people with "enormous frustration and anger" have contacted him about a legal challenge to the exit ban, he believes it would be "speculative".
"This is a scenario really in which the government holds all the cards because of the extraordinary powers it's got," professor Williams said. "You'd be a brave and perhaps wealthy person to mount the challenge."
"There is just no known right or entitlement for Australians to leave the country."
Professor Williams said governments blocking people from exiting the country was not a new concept, with alleged foreign fighters being prevented from leaving to join terrorist organisations.
"It's not that it's unprecedented, it's the scale of it that is so broad on a blanket basis."
Travellers have raised the question of how the government can justify someone leaving when the risk should be for the destination country to determine.
Professor Williams said the ban could be in place partially to stem the tide of Australians seeking to return home.
"For whatever reasons there's been a cap issue of the number of people able to enter [Australia]. Restricting exit is linked to that in not putting further pressure on those numbers."
Kate Ogg from the Australian National University's College of Law points out how the travel ban seemingly contravenes Article 12(2) of the International Covenant on Civil and Political Rights, which states: "Everyone shall be free to leave any country, including his [or her] own."
But Professor Williams said that argument was irrelevant because that international standard is not enforceable and does not form part of our domestic laws.
Beyond all the academic arguments, the question is, who would launch a legal challenge against the government on this issue?
"People don't bring court cases just for the intellectual exercise," Dr Beck said. "It'll be someone with a family motivation or a business interest [overseas]."