In the ongoing search of every constitutional nook and cranny for potential tactics to deploy against the Government, Dominic Grieve and his colleagues provoked an angry row by seeking to require nine named individuals to release correspondence on private channels relating to prorogation.

The lines write themselves. One side declares that it seeks only truth, and there’s definitely no element of wishing to intimidate, disrupt or harass the specific named people it is picking out, your honour. The other denounces the effort as an outrageous intrusion into personal privacy, an assault on civil liberties, and an effort to make Government an impossibly hostile environment in which to operate.

You may already have a preferred side in the debate; but the truth lies somewhere between the two.

First, the actual rules. The sought messages are widely described as “private correspondence”, meaning that (if they exist at all) they are alleged to be privately held, through personal accounts on various platforms, and on personal phones and computers. But there are circumstances in which such material can still legally be considered public.

To understand this, we need to look back to the early days of the Coalition. In particular to the Department for Education, between 2010 and 2012. Then the Financial Times and the DfE fought a battle over exactly this question: were ‘private” messages really private if they related to public officials doing their official work?

The battleground then was Freedom of Information – a journalist used the FOI Act to request emails which he knew existed, between named individuals (including Dominic Cummings, just like Grieve’s proposal). The Department replied that it did not hold the data – which was true, because it was held in private inboxes hosted by whichever email providers were being used.

The FT’s case was that this was a failure of the Department to hold (and thereby disclose) all the required data on its official work, not a failure of the FOI request. Ultimately, the Information Commissioner upheld the journalist’s appeal, and defined public employees discussing public work, no matter the medium used, to be public domain, not private correspondence. If you write down a note all about your work and take it home, it’s still work data – and the same goes under FOI for emails, texts, and so on.

So this might be correspondence on theoretically private media and deices, but if it’s on an official topic discussing public work, then it would generally fall under the definition of disclosable public data.

Of course, Grieve’s request was filed not through FOI channels but by the House of Commons as a Humble Address. Michael Gove’s reply declines to acquiesce essentially on the grounds that requiring such disclosure from civil servants would breach various items of legislation, which a mere Humble Address cannot in itself require the Government to do.

Ironically, Grieve could still therefore ask for this data under Freedom of Information. But that takes time: 20 working days to reply in some form, a limit which is often exceeded by many public bodies; possible debate about whether exemptions for things like policy development might apply, or how they weigh against public interest; and various other potential for delay and debate, followed by what is often a backlogged appeal process at the Information Commissioner’s Office. That would pose some obvious problems for a time-sensitive topic, which is presumably one reason why Grieve used a Humble Address instead (the other reason being the PR value of the Commons demanding something).

If he was to succeed in his argument, either on his chosen route or another one like FOI, there’s then a question of the practicality of enforcement. Chris Cook, the FT journalist in that DfE case, got the documents he was seeking – but a major reason why he was able to fight and win the case was that he already held proof that the out-of-department correspondence existed, including copies of some of it. Grieve claims to have reason to believe that privately-held public correspondence exists in his case, too – we don’t know how, or if he’s correct, but the question raises a difficult hypothetical scenario: how can we be certain that things which are meant to be disclosed actually are?

Even in response to normal, vanilla FOI requests, it’s often the case that public bodies seemingly fail to retain or properly disclose data even on their official records. I’ve filed FOI requests in the past knowing for a fact what the answer is, only to be told that the data doesn’t exist or to be given something completely different instead. We hope that officialdom will comply fully with its legal responsibilities, but the sad fact is that it sometimes does not. Often that is cock-up rather than conspiracy, but it would be naive to pretend that some organisations and individuals aren’t deliberately awkward.

That obviously gets more tricky when you get into the territory of disclosing officials’ correspondence from personal media and devices which may nonetheless amount to public data. Since the Cook/DfE case, ministers have confirmed that they will of course ensure public data is copied to public servers, but the blunt truth is that the fox is currently the gamekeeper: we reasonably expect public servants to abide by the law and the regulations of their jobs, but will they always reliably do so? And might there not be cases in which even their honest interpretation of what must be disclosed would be different to the view of their critics and opponents?

This swiftly gets into the issue of enforcement. If, as in this case, you’re talking about data the claimant believes to have been wrongly concealed in a private place when it should be public, you’re by definition starting off with a low level of trust in those who allegedly hold the data. Would Grieve trust his targets to fairly review and fully disclose voluntarily? Alternatively, whose job would it be – and in what route would they use – to secure the passwords to the named individuals’ phones, email accounts, WhatsApp accounts, Signal accounts, Facebook accounts and so on?

In what way will he or his enforcement agents ascertain that they have got all correspondence from all of the nine? I can chat to people via a messenger built in to Words With Friends, have conversations with other players on Call of Duty, or whistle coded messages as I pass someone’s house while on a stroll – what trawl is required, in the absence of a trust system, to obtain all public data within such channels?

You don’t have to go very far into thinking up options before it starts feeling rather hazardous. Should everything they hold of any sort just be surrendered as standard for adjudication as to its public or private nature? Would anybody ever agree to be an adviser ever again under such strictures? Who would do the adjudicating of the surrendered data’s status, which becomes more important at times of obvious controversy and distrust? What risks might there be to sensitive official data, genuine liberties of personal and family privacy for people working in public roles, including of political leaks?

We must assume such hazards are unintended potential consequences, rather than a deliberate form of intimidation of those being targeted, but they are undesirable nonetheless. They threaten and weaken the proposal: if the message to advisers is their critics do not trust them to disclose fully and properly, then they would predictably retort that they do not trust their critics to behave properly with such powers. Then we’re back to the original problem.

None of this is helped, of course, by the lack of structure around the route used. As a short term political tactic, the Humble Address does not even have the imperfect and often rickety protections and processes that you get on FOI, or the controversial and sometimes malfunctioning rules on criminal evidence disclosure.

Interestingly, even some of those former Tory MPs who lost the Whip last week appear to be aware of these problems. They haven’t criticised the tactic publicly, but it seems unlikely to be a coincidence that former ministers like Rory Stewart and Caroline Nokes voted against Grieve’s measure, while others including Philip Hammond abstained. They know how government works and can presumably imagine some of the downsides of such a tactic.