Australian mothers and children held in a Syrian detention camp will take the Australian government to court in an attempt to compel the government to bring them home.

Nine Australian women and 17 children – the wives, widows and children of slain or jailed Islamic State fighters – held in the Roj camp in north-east Syria, will file a writ of habeas corpus in the federal court on Monday morning, arguing that Australia has “effective control” of their detention and the power to set them free. The group members are all Australian citizens and argue they have a legal right to return to Australia.

Most have been held in squalid and violent detention camps more than four years: children are suffering from untreated shrapnel wounds, malnourishment and serious psychological illnesses. Some Australian children were born in the camp and know no life outside it.

Save the Children Australia, acting as litigation guardian in the case, said that legal action was “a last resort”, but it had been left with no choice but to take the Australian government to court “formally requesting … [it] stand by its moral and legal obligation to repatriate its citizens immediately”.

“This is a regretful but resolute action, borne of fear, suffering, frustration and despair,” chief executive of Save the Children Australia, Mat Tinkler, said.

Australia has already undertaken two successful repatriation missions from the detention camps in north-east Syria. In 2019, eight orphaned children, including a pregnant teenager, were returned to New South Wales from the camps.

And last October, four women and 13 children were brought back from Roj camp, also to NSW, with the government offering a commitment it would repatriate the remaining Australians when it was safe and officials were able to do so.

Of the women returned to Australia last year, one, Mariam Raad, has been charged with entering or remaining in a “declared area” in 2014 – Syria’s al-Raqqa province, which was then under the control of Islamic State – in breach of federal law. Her case is before a NSW court.

Tinkler said the elation and expectation raised by last year’s repatriation had been replaced by a bitter despair.

“The repatriations last October raised the remaining children’s hopes that they too would soon be out of harm’s way. Instead, they feel they have been abandoned by their country and are losing hope for the future.”

There is particular concern around a number of adolescent Australian boys. Boys, on reaching 11 or 12 years of age, are often separated from their families by the Kurdish forces running Roj camp, and taken to adult prisons, ostensibly out of concern over their potential radicalisation. The UN has repeatedly warned that boys taken from their families are at risk of being “forcibly disappeared, and subject to sale, exploitation, abuse [and] torture”.

One Australian teenager, Yusuf Zahab, died last year after being separated from his family. He was 11 when he was trafficked into Syria. The 26 Australians who are part of the legal challenge – not all of the 40-strong Australian contingent in Roj camp – are lodging a writ of habeas corpus in the federal court in Melbourne.

Their case will argue that the detention of the remaining Australian women and children in Roj camp is arbitrary and that Australia has effective control over their continued detention because the Syrian Democratic Forces that run the camp will, on the request of the Australian government, release the remaining Australians.

The challenge will argue Australia’s de facto control of the Australians’ detention is evidenced by the two successful repatriations they have mounted.

Similar habeas corpus cases have been run in Europe and the UK, not all successfully. A Canadian court ruled this year that the Canadian government was obliged to take steps to repatriate its citizens from Syrian camps.

None of the Australian women or children have been charged with any crime in any country – some women may face charges when they are returned to Australia – but the court challenge will argue their current detention is arbitrary and therefore unlawful.

The federal court writ, if it reached a hearing, could compel the government to justify why it has not repatriated its citizens.

When the last repatriation was undertaken, home affairs minister Clare O’Neil said the government considers a “range of security, community and welfare factors in making the decision to repatriate”.

The US-backed Kurdish forces, the SDF, which runs the camp, is anxious to empty the Roj camp of foreign nationals and is willing to assist with repatriation missions. Other countries, including the US, Germany, France, Sweden, Denmark and the Netherlands, have already safely repatriated dozens of children and their mothers from the camps.