News.   Nauru.   september 20.   photo by Angela Wylie.   pic shows asylum seekers off the HMAS Manoora setting themselves in the camp.   still with number tags.   fairfax.  digital.  ajw010920.003.003.

Asylum seekers on Nauru (faces not revealed for privacy reasons), wearing the tags they were given on arrival. Photo: Angela Wylie

There are increasing murmurings that the government's approach to asylum seekers is criminal, and even amounts to crimes against humanity. When I first heard this view, I was not convinced: ''crimes against humanity'' has a specific legal definition and, having worked at the International Criminal Tribunal for the former Yugoslavia in The Hague, I tend to be cautious when labelling behaviour as contrary to international criminal law. Yet, when you look beyond the rhetoric and to the legal elements, there appears to be an arguable case.

The International Criminal Court has jurisdiction over only the ''most serious crimes of concern to the international community'', including crimes against humanity. These are defined by the Rome Statute (the document governing the ICC's operation) as a particular act or acts, ''when committed as part of a widespread or systematic attack directed against any civilian population, with knowledge of the attack''. Acts that might be crimes against humanity include murder, deportation or forcible transfer of population, imprisonment, torture and ''other inhumane acts of a similar character intentionally causing great suffering or serious bodily or mental injury''.

This definition has a number of aspects to it, and proving crimes against humanity is difficult. A prosecutor arguing a case of crimes against humanity would need to prove, first, the acts (of murder, deportation, etc); second, that these acts were committed as part of a ''widespread or systematic'' attack; third, that this attack was ''directed against any civilian population''; and fourth, that these acts were committed with knowledge of the attack. This is a complicated crime, with several legal tests to pass before it can be established.

Unlike at other international criminal tribunals, there is no requirement that crimes against humanity be perpetrated during an armed conflict. This is important, because despite Prime Minister Tony Abbott's rhetoric equating ''stopping the boats'' with ''war'', it is unlikely that Australia could be said to be in an ''armed conflict'' with asylum seekers. For this reason, any charge of war crimes by the ICC could not be established, because proving war crimes requires the existence of an armed conflict.

The government policies that may amount to ''acts'' against asylum seekers could include transferring of asylum seekers to Manus Island or Nauru, as an act of ''deportation''. This is a forced displacement of people from an area where they are lawfully present, without grounds allowed under international law. This would require arguments about the legality of asylum seekers to access Australia's territorial waters and the legality of their removal from that area. However, the Refugee Convention - to which Australia is bound - is clear that there is an internationally protected right to seek asylum, and so it could be argued that the removal of asylum seekers from Australian territory is an act of deportation.

Conditions of detention could amount to ''other inhumane acts'' as a crime against humanity. The policies that limit access to medical treatment and to drinking water on Manus Island, and transfer non-malaria-immune pregnant women and young children to the high-malaria-risk area of Manus Island, could be argued to ''intentionally cause great suffering or serious bodily or mental injury''. The challenge would be establishing the specific ''intention'' to cause suffering or injury.

Recent allegations that the navy had inflicted burns on asylum seekers could amount to ''torture'' (again, if proved - the claims have been flatly denied by the Chief of Navy, Vice-Admiral Ray Griggs). Conditions of indefinite detention may be defined as ''imprisonment''. Finally, the reports of sexual violence on Manus Island could be argued to be an act of ''rape … or any other form of sexual violence of comparable gravity''. All are crimes against humanity.

It could be argued there is a ''course of conduct'' involving multiple acts, which is necessary to prove the attack against a civilian population. These acts are not isolated, occasional lapses: they are determined, widespread and systematic. In order to prove crimes against humanity, an attack must be done ''pursuant to or in furtherance of a state … policy to commit such attack''. The Australian government's acts regarding the treatment of asylum seekers are clearly in furtherance of state policy. Indeed, these acts are state policy.

Finally, to hold an individual responsible, their awareness of this widespread or systematic practice would also need to be established. Because Australia is a party to the ICC, its nationals can be tried by the court. The ICC tries individuals, not government policies as such, so it would be particular people who would be indicted by the ICC. This could be the responsible minister, or indeed the prime minister.

Given that many of these policies were implemented under the last government, it is possible that the former minister and prime minister could also be indicted.

Practically, there are a number of reasons why it is unlikely that any Australians will ever be charged by the ICC for Australia's treatment of asylum seekers, particularly regarding the ICC's limited resources, which mean it can only investigate and try a few cases. Given that this case would raise such new legal issues, it may not be a prudent use of resources to continue with this case. Only cases with a reasonable prospect of successful prosecution should be commenced: people should be subjected to legal proceedings only when a prosecutor is confident they can prove a case.

Yet while it is unlikely to ever be tried by the ICC, the possibility still exists. This course of conduct by the government may indeed amount to serious crimes, with individuals punishable under international law.

Sophie Rigney is a PhD candidate in International Criminal Law and Procedure at the Melbourne Law School. Between 2009 and 2011, she worked at the International Criminal Tribunal for the former Yugoslavia at The Hague, including for the standby defence counsel for Radovan Karadzic, and the defence of Lahi Brahimaj.

Twitter: @sophiejrigney