An apparent ‘constitutional aberration’ is to come under scrutiny from the Court of Appeal in the autumn. That, at least, is how it was described by the outgoing lord chief justice last month.

Lord Judge said the legislation he was referring to was not quite ‘a pernicious "Henry VIII clause", which enables a minister to override statute. But, unconstrained, it would have the same damaging effect on the rule of law’.

And what had moved Judge to use such striking language? It was the ‘statutory override or veto’ given to cabinet ministers by section 53 of the Freedom of Information Act 2000, enabling them to ignore disclosure rulings from any court in the land. The case has all the makings of a first-class constitutional clash. It is one thing for parliament to reverse the decision of a court. It is quite another for ministers to do so, even if they are acting under powers granted by parliament.

Our story begins in 2005, when Rob Evans, a journalist on the Guardian, made freedom of information requests to seven government departments. I should explain at this point that, although I write a weekly column for the Guardian, I have no involvement in this case and have not spoken about it to anyone at the newspaper. Evans wanted to see copies of letters that the Prince of Wales had written to ministers over the past six months, together with the government’s replies. According to the attorney general, Dominic Grieve, Prince Charles had been ‘particularly frank’ and the correspondence reflected his ‘most deeply held personal views and beliefs’.

The journalist’s request was eventually turned down by ministers on the basis that the information he had requested was exempt from disclosure. And the information commissioner agreed that publication would not be in the public interest. So Evans appealed to the Upper Tribunal, a superior court of record. His appeal was successful. The tribunal decided in September 2012 that what it described as advocacy correspondence – letters in which the Prince of Wales was advancing his views – should be disclosed. ‘The essential reason,’ said the tribunal, was that ‘it will generally be in the overall public interest for there to be transparency as to how and when Prince Charles seeks to influence government’.

At this point, you might have expected the seven government departments to have asked for permission to appeal. They did not. Instead, the attorney general played his trump card, issuing an ‘executive override’ under section 53. Grieve’s seven-page certificate reads very much like the arguments that the government put, unsuccessfully, before the Upper Tribunal. He explained the constitutional convention that the sovereign exercises prerogative powers on ministerial advice (the ‘cardinal convention’). From this it followed that the monarch had the right to be consulted, the right to encourage and the right to warn (the ‘tripartite convention’). In order to prepare for these responsibilities, the heir to the throne had the right to be instructed in the business of government (the ‘education convention’).

So much is uncontentious. But the attorney general rejected the Upper Tribunal’s conclusion that the advocacy correspondence was not covered by the education convention because it was not part of the prince’s preparation for kingship and was not the type of activity in which the monarch would engage. On the contrary, said Grieve, it fell within the tripartite convention’s reference to ‘warning’.

Since constitutional conventions are, by their nature, ill-defined, the point can be argued either way. Much more telling is Grieve’s view that, if disclosed, the prince’s letters ‘would potentially have undermined his position of political neutrality’ because he would be seen as disagreeing with government policy. ‘If he forfeits his position of political neutrality as heir to the throne,’ said Grieve, ‘he cannot easily recover it as king.’ In the attorney general’s view, the public interest in non-disclosure substantially outweighed the public interest in government accountability and transparency.

There is one safeguard, though: the veto in section 53 works only if the minister has reasonable grounds for his opinion. But Grieve did have such grounds, said the Administrative Court last month, dismissing the Guardian journalist’s application for judicial review. As Lord Justice Davis explained, the fact that the Upper Tribunal had reached a rational conclusion did not make the contrary view improper or unreasonable. A rather technical challenge based on the Aarhus Convention also failed.

I have some sympathy for Prince Charles, who no doubt regards his correspondence with ministers and others as confidential. I even have sympathy for Grieve, who was simply exercising powers granted by parliament under a previous government. But he had no need to do so. He could have let the law take its course and not protected the Prince of Wales from his outspokenness. Having strong views does not stop a prince becoming a wise constitutional monarch.