If Queensland wanted to withdraw its support of the Commonwealth managing the state's Murray-Darling Basin catchments, as Minister Andrew Cripps threatened yesterday, it would be a fairly straightforward political act. But the decision could have constitutional consequences that would test the High Court, legal experts tell Crikey. State governments have until July 9 to voice their concerns to the federal Water Minister about the current Murray-Darling Basin draft plan. With the final week of negotiations under way, Cripps told ABC Radio that his state would consider ending its referral of power of basin catchments to the Commonwealth. Victoria, South Australia and New South Wales also signed over the same referral of power in 2008. "Certainly what I'm saying is that the Newman government is considering the possibility of withdrawing the state government's 2008 referral of power to the Commonwealth to manage water resources in the basin and the reason that we have to do that is that we're still looking to see the details of the issues I've talked about," said Cripps. "If we can't have confidence in the work of the authority, then we'll find it very difficult to support the process and we must consider these options, including the withdrawal of the referral of power." It seems fairly straightforward for Queensland to implement such a decision, Paul Kildea, a lecturer at the University of NSW faculty of law, tells Crikey. Kildea explains that under the Water Act and the individual referral made by the state, it's clear that a state can withdraw its referral at any time. The Queensland government would be able to terminate its referral simply by having the governor issue a proclamation to that effect, as decreed in its original referral passed in state parliament. What happens if Queensland withdraws its support? "If they pulled out, then the ability of the Commonwealth to legislate over water resources would no longer be supported by legislation or authority," said Poh-Ling Tan, IWC professor of water law and governance at Griffith University. "The other states could do the same and then where would we be left?" This is partly a political move as states scramble to get their point of view across. "We're getting to business end of negotiations of the basin plan, and it may be that Queensland is using this as a negotiating tactic," said Kildea. "But it may also be a serious threat." Tan agrees that it may just be a political threat. "Queensland is just upping the ante," she said, noting it would be "unwise" for Queensland to withdraw. "You might disagree with the plan but it's like using a sledge hammer to completely break up the contract," Tan told Crikey. There are also wider implications. One of the key foundations of the 2007 Water Act and the state referrals of power was the creation of the Murray-Darling Basin Authority. "The MDBA has the ability to go over the top of the states and is able to enforce the Murray-Darling Basin plans. States have input and are consulted, but the authority is important and allows holistic management," said Kildea. If Queensland withdrew its referral of power, then the future of the MDBA would be in doubt. It would be able to manage water in South Australia, NSW and Victoria (assuming they didn't also withdraw their referrals of power), but not from upstream in Queensland -- completely undermining the objective of holistic water management, notes Kildea. Plus, states may think a proclamation from the state governor may suffice, but "there are some remaining questions about the capacity of states to withdraw referrals and their impact on Commonwealth legislation," said Kildea. "It's possible that Queensland's withdrawal of power could be challenged by somebody in the High Court. "With these sorts of things you pull on a thread and all sorts of other things unravel," he told Crikey. "There are some constitutional questions which haven't been addressed by the High Court, it hasn't had the opportunity to do so, and there's it's quite possible it may open up an opportunity to test some of those questions." At a meeting of state water ministers last Friday, it was agreed that the Murray-Darling Basin Authority would run modelling on a sustainable diversion limit of 3200 gigalitres. NSW, Victoria and Queensland have all declared that the current number of 2750 gigalitres is too high and will have a detrimental economic effect on basin communities. South Australia is currently the only state calling for more water to be returned to the river system. The Murray-Darling Basin Authority confirmed that it has begun to run modelling on the 3200 gigalitres figure. It usually takes at least three months to run a figure through the MDBA's modelling. Tony Burke's office tells Crikey the minister still intends to have a basin plan in place by the end of the year, regardless of whether this latest modelling is finished.