The full background to the PSNI’s pursuit of television journalists Trevor Birney and Barry McCaffrey, using a proxy, in the form of the Durham police force, to arrest the men, has yet to be revealed.

But on its face, it seems the authorities are attempting to characterise as ‘theft’ the journalists’ acquisition of documents from the Police Ombudsman’s office in Belfast dealing with the 1994 Loughinisland massacre.

The television documentary on the Loughinisland killings that they produced,  ‘No Stone Unturned‘ – with Alex Gibney as director – was a masterpiece of investigative journalism which revealed a disturbing level of official participation in the cover-up cum incompetent police investigation of the UVF killing of six Catholics watching the World Cup in their local bar.

The documentary highlighted a shocking level of collusion between the local RUC and the killers which went undiscovered in the subsequent investigations, one of which was led by the Police Ombudsman’s office, then headed by different management.

Journalists come across documents all the time, including documents from government offices. Sometimes the leaks are authorised, just as often they are not. But I cannot recall an instance of a leak being described as ‘theft’.

The PSNI/Durham police portrayal of the documentary makers’ acquisition of Police Ombudsman documents as larceny means that Birney and McCaffrey could now be charged with theft, or at the least with receiving stolen goods?

Meanwhile the PSNI’s failure to pursue those in uniform who covered up the slaughter – as well as the killers and their accomplices – stands in stark contrast to this belligerent pursuit of the two film-makers.

This is a development that must be resisted by all journalists in Ireland, no matter what medium they work in. To charge or pursue the makers of ‘No Stone Unturned‘ for doing their jobs represents an unprecedented existential threat to Irish journalism in all its forms.

The truth of what happened in Loughinisland in 1994 took more than two decades to emerge. That it did so was due to the ability of the film-makers to persuade those with knowledge to share it with their viewers and the courage of their sources to reveal what they knew.

That they did so was a tribute not just to their reporting skills but to the bravery of their sources.

Make no mistake, this move by the PSNI is directed not just at journalists but also at their sources, perhaps especially their sources.

There are other Loughinislands yet to be uncovered, some the responsibility of the state, others committed by their enemies.

If journalists are to face the threat of prosecution for acquiring documents which those in power would prefer to keep hidden, then the truth will never be told about Northern Ireland’s tragic past. Instead anger and resentment will fuel the fires of bitterness and rancor.

The track record of Irish journalism in resisting official censorship – and its close cousin, self-censorship – is not, sadly, a good one. This is one test, however, that cannot and must not be flunked.

This pithy review of ‘No Stone Unturned’, from The Guardian, tells you all you need to know about why the PSNI have moved against the film-makers: