If Australia has returned Sri Lanka Tamils to the Sri Lankan military, before assessing their claims, there are legitimate questions about whether we are acting beyond the scope of Australian law, writes Michael Leach.

Reports that Tamil asylum seekers picked up by Australian authorities may have been handed over to the Sri Lankan navy raise a lot of questions.

Given the obsessive culture of secrecy under Immigration Minister Scott Morrison's watch, few are easily answered. If the reports are true, one is whether the Minister's actions would be found lawful if tested in the High Court.

Critics and defenders are fond of making different arguments about the status of the Refugee Convention in national law. For example, Australia's offshore refugee program is not required under the Refugee Convention: it is a voluntary and in the main generous program.

The Convention is more focussed on what we call onshore asylum seekers. Policies that treat onshore arrivals differently to offshore refugees - such as the former temporary protection visa - have been criticised on several grounds, but such differential treatment in itself does not appear to breach the Convention, except where asylum seekers have travelled directly from their country of origin. With the exception of a few West Papuans, this has not generally been in the case in Australia.

However, there is one very clear principle in the Refugee Convention: it prohibits the refoulement (or return) of asylum seekers to the country where persecution is alleged to have taken place without assessing claims for protection. Article 33 states that:

No Contracting State shall expel or return ("refouler") a refugee in any manner whatsoever to the frontiers of territories where his life or freedom would be threatened on account of his race, religion, nationality, membership of a particular social group or political opinion.

This article is the very foundation of the Convention. To directly return Sri Lanka Tamils to the Sri Lankan military, before assessing their claims could scarcely be a more flagrant and direct breach of this commitment.

The principle of non-refoulement is also enshrined in the Convention Against Torture. Some experts argue that returning refugees to a state practicing torture could constitute becoming an accomplice to that crime. Further prohibitions on refoulement can be found in the International Covenant on Civil and Political Rights, and the Convention on the Rights of the Child. Australia is a signatory to all of these.

Some argue that the principle of non-refoulement is so established as to have become customary law, though as Australia is a signatory to the conventions noted above, this is not required.

Recognised exceptions to the principle of non-refoulement are few, and include situations of mass influx, or where there is a danger to the security of the country amounting to "grave and imminent peril", or where particular asylum seekers are known to have committed serious crimes. None of these exceptions would appear to apply to the current situation, and some could only be established by processing asylum claims.

In 2011 the High Court found the Gillard government's proposed "Malaysia solution" to be in breach of the Australian Migration Act, which had incorporated the principle of non-refoulement. The government had proposed the return of certain asylum seekers to Malaysia as a "safe third country". The Court ruled that despite a Ministerial decree to this effect, Malaysia was not such a country under Australian law, as it was not a signatory to the Refugee Convention.

The Migration Act has since been amended, with a much less stringent "national interest" test on the transfer of asylum seekers to other countries. However, without explicit parliamentary authorisation, these sorts of ministerial actions still remain open to High Court challenge, as was made clear last month when the High Court struck down the Minister's attempt to cap the number of permanent protection visas offered to asylum seekers already in Australia.

Whether the new Senate would allow regulations facilitating direct refoulement of this type is questionable. In addition, the issue of retrospectivity would arise, and any such amendment might also be construed internationally as a de facto repudiation of the Convention.

Irrespective of the complex legal position, there are broader political and moral considerations here.

While Sri Lanka has not ratified the Rome Convention, and is not subject to the International Criminal Court (ICC), other measures are now firmly in train. The UN High Commissioner for Human Rights has announced a major 10-month investigation into genocide and war crimes committed during the Sir Lankan civil war, with the aim of establishing "the facts and circumstances of such alleged violations and of the crimes perpetrated with a view to avoiding impunity and ensuring accountability ".

Members of the US Congress are currently lobbying for entry restrictions for any Sri Lankan government or military figures responsible for war crimes.

Given these developments, PM Abbott's defence of Sri Lanka's progress on human rights and peace is pre-emptory at best; and given allegations of ongoing human rights abuses, insincere at worst.

The Human Rights Law Centre has already described Australia's relationship with Sri Lanka's government as "dangerously close": motivated to secure co-operation with its asylum seeker policies, with agreements already in place for the involuntary return of rejected asylum seekers.

The Sri Lankan government was also grateful for Australia's "bold" decision to oppose a war crimes tribunal, and not to co-sponsor the now successful UN resolution. While Canada and India boycotted last year's CHOGM in Sri Lanka over the issue, and the British PM openly condemned the regime's stance on human rights, Australia provided the regime with two patrol boats, and diplomatic cover.

Given that the new UN investigation is backed by the United States, the Abbott Government's position clearly puts us at odds with our friends and allies.

This raises wider questions. When does border protection cross the line to becoming an accessory to human rights abuse? Could Australia's refoulement of Tamils later be investigated by the forthcoming UN inquiry? And back at home could these ministerial actions later be challenged, despite subsequent changes to the Migration Act? Is "operational silence" facilitating acts that may be found unlawful?

These issues may also raise complex issues for those acting under ministerial orders. The advice prepared by Defence Legal Services on the lawful parameters of Royal Australian Navy action should be tabled in Parliament. It's time to break the operational silence, as there are legitimate concerns that the Minister is acting beyond the bounds of well-established international principles, and may be acting beyond the scope of Australian law.

Michael Leach is associate professor in politics and public policy at the Swinburne University of Technology. View his full profile here.