Attorney General John Larkin has advised the Executive that it can overrule Environment Minister Alex Attwood's planning decision that led to John Lewis pulling out of Northern Ireland.
First Minister Peter Robinson said advice from the Executive's chief legal adviser meant that there was still hope that the high-end retailer would reapply to set up shop at Sprucefield outside Lisburn. He said it would have implications for other decisions which were "controversial, significant, cross-cutting or which is novel".
"Alex Attwood said it was his decision and nobody could overrule him. I indicated he was wrong.
"I am now satisfied on the advice of the Attorney General that he does not have such an authority. The authority lies with the Executive," the First Minister said.
Pushing home the general implication, he added: "Whether ministers like it or whether they don't, that was what was negotiated at St Andrews and that is what the law says.
"Those decisions can be called in for the Executive to decide on."
John Lewis, the high-end department store, had planned to build a superstore and its Irish distribution hub at Sprucefield near Lisburn.
Last month Mr Attwood advised a planning tribunal that general stores should be located in Belfast, not at out-of-town shopping centres like Sprucefield, which is designated a Northern Ireland regional centre.
Mr Attwood had hoped to attract John Lewis to the Royal Exchange development in a bid to boost Belfast city centre.
In theory, the planning tribunal could have ruled against him, but that seemed unlikely. As a direct result John Lewis pulled the £150m, 1,500-job development.
Mr Attwood's comments were based on a reading of the Belfast Metropolitan Area Plan (BMAC).
"It is the Belfast Metropolitan Area plan that is going back to the Executive," Mr Robinson said.
"Alex Attwood took a view on how BMAC should be applied, but now what happens will be a decision for the Executive to take.
"If there is a different outcome it may lead John Lewis to reapply."
Mr Robinson said the Executive would take its time over the issue to ensure that proper and fair procedures were followed.
"The Executive have to take a decision on this matter, and to proof itself against any possible legal challenge they need to take all of the steps and interrogate the issue in the same way as an individual minister would do. They may even need to bring in departmental experts to take them over the issue," he stated.
It is understood that Mr Attwood sought a meeting with the Attorney General, who is the Executive's chief legal adviser, before the decision was taken.
Under the 1998 Good Friday Agreement ministers had almost total autonomy within their departments. However, the law was amended following the St Andrews Agreement which the DUP and Sinn Fein concluded in 2006.
The advice threatens to put a dent in the so-called silo system whereby Executive ministers have considerable autonomy in their own departments.
The larger political question will be whether the SDLP will reconsider its position on the Executive and consider going into opposition if Mr Attwood is over-ruled on such a fundamental decision.
He has been asked to present his papers on the planning decision over John Lewis to the Executive.