International law expert Dr Gideon Boas said an overhaul of Australia's domestic law to allow the ADF more freedom to target Islamic State fighters in Iraq and Syria could have the potential to lead to "excessive civilian damage".
The Monash University academic's comments come after last week's announcement by Prime Minister Malcolm Turnbull on changes to the Criminal Code in regards to bombing the militant group.
The overhaul would protect Australian Defence Force members from being charged with war crimes for bombing IS militants not directly involved in fighting.
Mr Turnbull said that, under current legislation, military personnel could potentially be liable to prosecution under domestic law for the death of a person who was "not causing hostilities."
Alongside Defence Force Chief Mark Binskin, Mr Turnbull told reporters that the legislation change would bring Australian law into line with international law in the fight against IS, or Daesh.
"Under international law, all members of an organised armed group such as Daesh can be targeted with lethal force, subject, of course, to the ordinary rules of international humanitarian law," the Prime Minister said last week.
"This is a reasonable and conventional approach adopted by the armed forces of our key allies across the world. But there is a legal argument that Australia's domestic law is more restrictive than international law. This legal risk posed a major challenge to the effectiveness of our operations."
Australia's role in fight against IS
Australia is a key ally of a United States-led bombing coalition targeting IS in Iraq and Syri.
The ADF has now been part of the operations in the Middle East for two years.
Dr Boas explained that the law on operations against a terrorist organisation was covered in various Geneva conventions and customary international law.
It is binding on all signatory countries.
He said although there is a gap between Australian and international law on the matter, the risk the prime minister referred to is small.
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"There is a prospect that, under Australian domestic law, if the conduct of the soldier engaging in the targeting was reckless as to the injury or death of a civilian person, then there's a prospect of prosecution," Dr Boas told SBS.
"Now the likelihood of that occurring is probably minimal, and I gather from what's been said in parliament that this is really just designed to cover off the unlikely event that an allegation of that kind, or a prosecution of that kind, might occur."
Dr Boas considered the reasons for the change legitimate, but said the announcement left some ambiguity and could potentially have devastating consequences.
He added that, if the laws are overreaching, heavy civilian casualties resulting from Australian bombing raids could happen with no legal accountability.
"It's a legitimate concern, and it's a change that could legitimately be made," Dr Boas said.
"I think we need to see the detail of the law that's proposed. If what's being proposed here is simply encapsulating the principles of international humanitarian law, there are built-in safeguards there.
"If it's proposed that the laws go further than that, and in some way immunise soldiers and officers from targets - or from the outcome of targets - that have a military objective but have an excessive civilian-damage component, then that's of grave concern and we should do something about that."
Is it a question of ambiguity?
Military law expert David Letts says the changes are not a cause for alarm.
The Australian National University academic believes the government clearly stated its purpose.
"Certainly, the clarity, in terms of what the government has said it wants to amend, yeah, I think that's quite clear," Professor Letts said.
"It certainly is not a broad, sweeping announcement that Australia is going to amend its domestic law so that targeting can be of such a width that, as a matter of course, there would be civilian casualties involved in Australian military operations. There's no suggestion of that at all."
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Professor Letts said he thinks the only ambiguity is related to which specific section of the Criminal Code will be overhauled.
"The grey area is that the government, in the announcement, has not tabled what the precise amendments to the Criminal Code are," he said.
"So that's the source of speculation, if you like, that, until that is tabled, until there's a bill that's put before the parliament, the precise nature of the changes are not clear. But the statement from the prime minister and the minister for defence clarifies that as much as possible in the absence of a bill before the parliament."
The Greens respond
Greens senator Scott Ludlam agreed with Dr Boas that the announcement left much unanswered.
Senator Ludlam said he believes the finer details will not be known until the bill is tabled, meaning fears for civilian life will receive little parliamentary debate or independent analysis.
"Parliament is sidelined. Committees are sidelined. There's no real possibility until after the fact of establishing why these changes are needed," Senator Ludlum told SBS.
"The main issue we have, really, is that it potentially opens up greater risks to civilian casualties in a place where it's already formidably difficult to establish what's going on as a consequence of the bombing campaign, and we don't really quite see how the case is being made that this is a necessary change.
"Now, it may be that it's entirely justifiable, but, from our point of view, anything that potentially changes the definition of war crime involving civilians who might be in the way when bombs are dropped is due proper scrutiny."
SBS approached the office of Defence Minister Marise Payne for comment.
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