Just as Australia’s new special drought envoy, Barnaby Joyce, was proposing this week to raid the already dangerously low Murray–Darling water flows in the name of the drought, the federal and South Australian governments succeeded in cutting off an investigation into how the situation in the river system got so dire in the first place.

The governments used legalities and delay tactics to stop the commissioner, Bret Walker, SC, from forcing important witnesses to give evidence at the South Australian Murray–Darling Basin Royal Commission, working in concert to ensure the High Court could not hear a case that would have determined if Walker had the authority to compel them.

As a result, the court case – which would have been a landmark test case on state-to-state and Commonwealth-state relations – has collapsed.

The roadblock came as Joyce argued that, because the drought was an emergency, more of the environmental water that is legally retained to stop the rivers drying up should be released for irrigators instead, to grow fodder for starving livestock. He said the crisis justified ignoring the law and taking the water, comparing the situation with people trying to save their properties in a bushfire not bothering with legalities.

“They don’t come and knock on your door and say, ‘Can I borrow your bulldozer, can I borrow your car?’ ” Joyce told ABC Radio National. “They just take it, because it’s a national emergency … Now this, as far as I’m concerned, is a national emergency.”

Joyce said the water the government had purchased under the Murray–Darling Basin Plan to maintain the health of the river flowed right past irrigators’ properties and should be diverted.

His comments drew a warning from Emma Carmody of the New South Wales Environmental Defenders Office that the water could not be taken, legally, without changes to the Water Act.

Once Walker knew he couldn’t fulfil his legal obligations to the witnesses and therefore couldn’t hear the evidence his summonses were seeking at all, he was obliged to notify the High Court and the federal government.

“The Commonwealth Environmental Water Holder who is responsible for managing that water, which was purchased with taxpayer money, is bound by a specific set of obligations in the Water Act,” Carmody said in response.

The water could only be sold for a “legitimate purpose”.

“And that basically is limited to circumstances where it isn’t required for the environment,” she said.

As debate continued over Joyce’s proposal, the SA and federal governments succeeded quietly in ensuring the state’s royal commission into the management of the Murray–Darling Basin Plan could not hear from whistleblower witnesses.

The federal government’s refusal to let current and former officials of the Murray–Darling Basin Authority and the Commonwealth Scientific and Industrial Research Organisation give evidence has now forced the withdrawal of summonses the commission had issued.

Therefore, these officials can’t be forced to answer questions about why so much water has been taken out of the river system, against scientific advice, over the past almost-decade.

Commissioner Walker had summonsed the head of the MDBA, Phillip Glyde, along with other officials.

The SA Royal Commissions Act provides the power to compel witnesses, but the federal government was arguing before the High Court that the power did not extend to Commonwealth officials.

After preliminary hearings earlier this year, and ahead of a scheduled full-bench hearing in October, the government withdrew its case formally on Wednesday.

The move was part of a catch 22-style trap that ensnared the royal commissioner, created by the actions of two Liberal governments that don’t wholly support his inquiry, which was established by the previous SA Labor government before it lost office.

The new SA government forced Walker’s hand by refusing to grant the extension to his reporting deadline he needed to afford the witnesses the procedural fairness legally required, in the event they were forced to give evidence.

Because the High Court could not hear the case until October 9, even if it eventually found in his favour, Walker would not have enough time to deal properly with the witnesses’ evidence and report by the deadline – unless the deadline was extended.

If he couldn’t deal with the witnesses fairly, he was obliged legally not to receive their evidence at all. He explained this to the SA government in a series of increasingly forthright letters last month.

Despite the fact the state government was a co-defendant in the case, representing the interests of the people of SA and knowing how crucial an extension of time was to the royal commission’s ability to get to the bottom of the alleged water mismanagement, it refused Walker’s request.

Once Walker knew he couldn’t fulfil his legal obligations to the witnesses and therefore couldn’t hear the evidence his summonses were seeking at all, he was obliged to notify the High Court and the federal government.

This is because that information turned the subject of the High Court case into a hypothetical one, without any real effect.

And that, in turn, meant the court would not agree to hear it at all, as it only determines cases where the result will have an effect, not on matters of principle.

That led to the case being withdrawn.

In other words, the combined actions of the two governments in using legal push-back and delay tactics created the situation and blocked the commission’s access to evidence.

Counsel assisting the royal commission, Richard Beasley, SC, announced the end of the court proceedings – and laid out the sequence of events – during a commission hearing in Adelaide on Wednesday afternoon.

He suggested there were other officials subject to the now-withdrawn summonses who were eager to tell what they knew – but could not do so without an order.

“Relevant witnesses who are in the nature of whistleblowers want to give evidence to this commission but are not willing to do so unless compelled,” Beasley said.

Addressing the commissioner, he said: “It is a matter for you what inferences you draw from the failure of the government to grant that extension.”

The summonses had also sought Commonwealth documents, which SA Centre Alliance senator Rex Patrick is now seeking separately through an order of the Senate.

Fellow SA senator, independent Tim Storer, has also been pressing the government separately in parliamentary committee hearings on the reliability of its existing water-accounting practices.

Two water scientists who gave evidence to the royal commission on the amount of water being wrongly allocated, lost and stolen from the rivers had their research into how irrigation efficiency was being used to reduce flows even further published last week in the prestigious international journal Science.

The paper, co-written by Australian National University professors Quentin Grafton and John Williams and other hydrologists, warns that increases in irrigation efficiency – such as lining aqueducts to stop leakage – “must be accompanied by robust water accounting and measurements, a cap on extractions, an assessment of uncertainties, the valuation of trade-offs and a better understanding of the incentives and behaviour of irrigators”.

Shortly after Barnaby Joyce aired his proposal on morning radio, the royal commission also heard from a witness who said the current legal structure surrounding water allocations was there precisely to prevent proposals of the kind being put forward by the special drought envoy.

Juliet Le Feuvre, from non-government river campaigners Environment Victoria, told the commission she was concerned politicians might cut across the role of the independent government-appointed Commonwealth Environmental Water Holder, established to manage the Murray–Darling water entitlements for the environment.

“We and the other environment groups fought long and hard to get the water holder set up, to take decision-making about the use of environmental water out of government hands and into an independent entity like the water holder,” Le Feuvre said.

“It was to get it away from that political process where it could be bartered away when times got tough … That’s the point about the water holder … They should be making decisions in the best interests of the environment and not be subject to political interference. There’s a great temptation for ministers and others to get involved and try to direct them in what they should be doing, but they should not be swayed by those considerations.”

Le Feuvre acknowledged the drought’s impact on agriculturalists.

“It’s not that the irrigators don’t have a need,” she said.

“Obviously it’s a really difficult time for everybody and there are farmers who are really struggling to finish off their crops. It’s not taking anything away from the situation that they find themselves in. But the environment needs water too, particularly in New South Wales where a lot of the calls are coming from.”

Commissioner Walker addressed the Joyce proposal directly.

“As recently as this morning, there has been a suggestion made that water for irrigation from that held for the environment should be taken in the same way as a private bulldozer is taken by firefighters during an emergency,” Walker said.

“That is, without any permission or consultation, just taking it because it is an emergency.”

He asked Le Feuvre if she had heard such a suggestion before.

She replied she hadn’t, but noted that Victoria had the legal power to divert water from the environment to irrigators and others during droughts and fires.

Earlier in the week, Joyce had also cited a NSW government decision to divert 15,000 megalitres of water to farmers – a move apparently allowed similarly under NSW law.

But Le Feuvre said strict rules governed such moves, designed to protect the environment.

“I mean, if a tanker arrived and said to an irrigator, ‘Sorry, I’m emptying your dam because Joe down the road needs it’, they would be pretty upset,” Le Feuvre said. “And exactly the same reasoning applies to the environment.”

Walker responded: “It would be an offence.”

The witness agreed. Walker asked her a second time, just to be sure, whether other than the state-level situation she had described, she had ever heard of such a proposal to divert environmental water.

“No, I’ve never heard of it,” Le Feuvre said.

That’s because no such diversionary power exists for the federal government under the current Water Act, something Walker and Joyce both know.

Despite the legal setback to his inquiry this week, it would appear the royal commissioner does not intend to back off – even if that puts him at odds with governments and, in particular, the newly minted special envoy for the drought.