The ruling found people on casual contracts working "regular, certain, continuing, constant and predictable" hours are entitled to paid leave benefits.
Advocates say a landmark court ruling on casual workers' entitlements could be a game changer for international students.
On Wednesday, the Federal Court found casual staff working predictable hours with a firm advanced commitment did not meet the definition of casuals and, therefore, were entitled to annual leave, sick leave and carer's leave.
Co-founder of Student Jobs Australia and former president of the Council of International Students Bijay Sapkota said the result had the potential to reduce the exploitation of international students in the casual workforce.
"Before this pandemic, many casual international student workers told us they felt forced to go into work even when they were sick, otherwise they would risk losing their job or income," he told SBS News.
"So this could create a fair work environment for everyone in the community and also help increase international students' employability and job security."
The Federal Court case was brought by coal mine worker Robert Rossato who successfully argued his three-and-a-half year stint with labour company WorkPac was a permanent role disguised as casual work.
Mr Rossato worked on six different contracts at Glencore mines on a casual contract, at one point working 12-hour shifts for seven days straight followed by seven days off.
Justice Mordecai Bromberg said that pattern constituted "regular, certain, continuing, constant and predictable" work, rendering the nature of his employment permanent, not casual.
While international student advocates have welcomed the ruling, big business is now lobbying the federal government to stop workers from "double dipping" in entitlements.
Industrial Relations Minister Christian Porter said the decision would have immediate implications for businesses at a time when many had taken a huge hit from coronavirus.
He said the government would consider joining an appeal.
"Given the potential for this decision to further weaken the economy at a time when so many Australians have lost their jobs, it may also be necessary to consider legislative options," Mr Porter told AAP.
But Labor's industrial relations spokesman Tony Bourke said it was employers who had been "double dipping", saying he was "astonished" by the governments reaction to the ruling.
"If [employers] have been refusing to give employees the security that they were legally entitled to, then the last thing the parliament should be doing is acting as a protection racket to cover for people who have broken the law," he said.
"A whole lot of people, particularly casuals, have found themselves with nowhere to go during COVID-19, have found themselves not entitled to a whole lot of what is offered to people in permanent work."
Employers fear a flood of class actions could result in backpay claims of up to $8 billion.
International student groups are also pushing for work limits to be relaxed.
Mr Sapkota said international students were employed as casuals because their visas come with a limit of 40 hours' work per fortnight - or 20 hours per week - which does not quite add up to three full shifts at most workplaces.
"A lot of employers wanting to recruit international students cannot because they can't work three full days a week, so if we can lobby to increase the work restriction from 20 hours to 24 hours then that alone could create tens of thousands of part time jobs for students," he said.
"That's one of the biggest problems international students face, and a lot of employers use that restriction on their working hours as a way to exploit international students by threatening to report them to Home Affairs."
With additional reporting from AAP