GORDON Lyons breached Stormont's ministerial code when he took last Friday's unilateral decision to halt work on permanent inspection posts at the north's ports.
The attorney general is understood to have confirmed that the DUP minister should have consulted with his executive colleagues before making the announcement.
Under the ministerial code, policy that is deemed cross-cutting and controversial should be presented to the executive for consideration beforehand.
When ministers met yesterday Mr Lyons was asked to bring a paper on his proposal to the executive, which is due to meet again tomorrow, as well as spell out what action he had actually taken.
The agriculture minister later told the assembly that checks on goods at ports were continuing, while his department last night failed to respond to a query from The Irish News which sought to establish what work had already been undertaken and what Mr Lyons had in reality halted.
He defended Friday's decision in the assembly chamber and listed a series of problems that he said had arisen since the protocol was implemented at the beginning of the year, including additional bureaucracy, a reduction in consumer choice, and problems bringing guide dogs across the Irish Sea.
Mr Lyons said the Irish Sea border had created "fundamental concerns and challenges".
"It is so, so important that we get an alternative to the protocol," he said.
"No amount of tinkering with it is going to make it work - it needs to go."
Deputy First Minister Michelle O'Neill insisted Mr Lyons required executive approval and said he had made no formal proposal to fellow ministers.
"The executive's position remains that it's our duty to implement the protocol, it's clear that any move to change that position would require an executive decision," she said.
"The agriculture minister has yet to bring a proposal to the executive to change the status quo and if he does so then clearly we will engage in that.
The Sinn Féin deputy leader said it was her understanding that beyond Mr Lyons' instruction nothing had changed operationally at the ports.
But First Minister Arlene Foster insisted her colleague's decision could only be overturned by a court.
Mrs Foster rejected the suggestion that Mr Lyons could be overruled by the wider Stormont executive.
"Gordon has taken the decision based on evidence and law that he has looked at and the decision still stands until it is overturned by a court," she said.
"I know that others take contrary views in relation to that, but that has been the position when other decisions have been taken by ministers in the past which have had to be taken to court and given the determination there.
SDLP MLA Matthew O'Toole said Mr Lyons' decision was "reckless, pointless and wrong but it is also on unsafe legal ground".
"Every member of the executive has a legal responsibility to implement the protocol, whether they choose to admit it or not," he said.
"The DUP has chosen to be dishonest with people, they have chosen to pretend that they can rip up the protocol and do whatever they want – that is wrong."
Alliance deputy leader Stephen Farry said any decision needed to be taken by the executive collectively.
"Any solo run would be a breach of international responsibilities, and while also being significant and cross-cutting," he said.
