Three Western war crimes investigators turned up to see me in Beirut last week. No, they didn't come to talk about the Bosnian war. They wanted to know about torture at Israel's notorious Khiam jail in southern Lebanon, about beatings and imprisonment in cupboard-size cells and electrodes applied to the toes and penises of inmates under interrogation. Most of the torturers were Lebanese members of Israel's proxy "South Lebanon Army" militia, and they performed their vile work for the Israelis – on women as well as men – from the late Seventies until Israel's withdrawal in 2000: almost a quarter of a century of torture. Khiam prison is still there, open to the public, a living testament to brutality and Israeli shame.

The problem is that Israel is now trying to dump its Lebanese torturers on Western countries. Sweden, Canada, Norway, France, Germany and other nations are being asked to give citizenship to these repulsive men in the interests of "peace" – and also because the Israeli government would prefer they left Israel. The three investigators – two cops and a justice ministry official – had come to Beirut to make sure that their government wasn't about to give citizenship to Israel's war criminals. And they knew what they were talking about. We both knew that one former torturer was living in Sweden with his two sons, and that another had opened two restaurants in America.

And I was happy to chat to them. But chatting is one thing. Testifying is quite another. I make this point because the BBC told me last week that their Belgrade correspondent, Jacky Rowland, was planning to testify against Slobodan Milosevic at The Hague war crimes tribunal. I was invited this week to participate in a BBC radio interview with yet another BBC man who had given evidence at The Hague, Dan Damon.

And, in fact, I received a phone call from one of The Hague investigators a few weeks ago, wanting to know if I had accompanied a European Union delegation to a Bosnian concentration camp in 1982. I had travelled with the EU men to two camps – not the one that The Hague investigator was interested in. But this was not the first call I've had from The Hague and I pointed out this time – as I had before – that I didn't believe journalists should be policemen. My articles could be used by anyone at The Hague and I was more than ready to sign a letter to the effect that they were accurate. But that was all.

So when Dan Damon of the BBC argued on air this week that the written or spoken report might not be "believed" if a reporter wasn't ready to testify in a court, I was a bit taken aback. In many cases, The Hague has commenced proceedings against war criminals on the basis of newspaper articles and television programmes. No one, so far as I know, has ever questioned our reports on Serbian, Croatian – and, yes, Muslim Bosnian – war crimes. In fact, I suspect Dan's argument was a bit of a smokescreen to cover his own concern about the boundaries of journalism.

I know, of course, how the arguments go. I may be a journalist, says the reporter as he or she turns up to the court, but I am also a human being. A time must come when a journalist's rules are outweighed by moral conscience. I don't like this argument. Firstly, because the implication is that journalists who don't intend to testify are not human beings; and secondly, because it suggests that reporters in general don't normally work with a moral conscience. Jonathan Randal, who worked for The Washington Post in Bosnia and has told The Hague tribunal that he will not testify against a Serb defendant, understands this all too well.

What worries me, though, is that journalism includes an element of masquerade if we cover wars as reporters and then participate in the prosecution of the bad guys at the request of a court whose writ extends only to those war crimes which it sees fit – or which the West sees fit – to investigate. Jacky Rowland of the BBC, for example, did not – while reporting the Balkan atrocities – turn up on Serbian assignments with the words: "I'm from the BBC and – if your lot lose – I'm ready to help in your prosecution". Indeed, if she had said that, she wouldn't have had the chance to undertake many more reporting assignments. Nor would any of us. But – if it's now going to be the habit for BBC reporters to turn up as prosecution witnesses at The Hague – heaven spare any of us in the future.

Now I have nothing against Jacky Rowland's reports. And if she feels her testimony is vital to convicting Mr Milosevic, that's up to her. But this story has another side. For Ms Rowland is not planning to attend The Hague court because she has chosen to give evidence against the former Serb leader. She is travelling to The Hague because the Western powers have decided that she should be permitted to testify against Mr Milosevic – though not, of course, against alleged war criminals of equal awfulness in other parts of the world.

Let me explain. Over 26 years, I've seen many war crimes in the Middle East. I was in Hama when Syrian Special Forces were killing up to 20,000 civilians during a Muslim revolt in 1982. I was at the Sabra and Chatila camps the same year when Israel's Phalangist thugs were butchering 1,700 Palestinian civilians. I was with Iranian soldiers when Iraqi troops fired gas shells into them. I was in Algeria after the throat-slitting bloodbath of Bentalha, for which Algerian soldiers have since been implicated.

And I believe that those responsible for these atrocities should be put before a court. Rifaat Assad, the late Syrian president's brother, was responsible for Hama. He lives in Spain. But of course, no one is planning to put him before a court. Ariel Sharon – held "personally responsible" by his own country's inquiry into Sabra and Chatila – is now the Prime Minister of Israel. The Iraqi army is safe from prosecution – indeed, we are inviting it to overthrow Saddam Hussein.

So if any reporter wants to testify against the above gentlemen, they can forget it. Ms Rowland will not be invited to put Mr Assad or Mr Sharon behind bars. In fact, Belgium has just done its best to stop the survivors of Sabra and Chatila from ever testifying against Mr Sharon in Brussels.

And there you have it in a nutshell. We journalists are not being asked to testify in the interests of international justice. Ms Rowland is going to testify against a criminal whom we now wish to try; and we should remember that back in 1995, when we needed Mr Milosevic to sign the Dayton agreement, Ms Rowland was not wanted by The Hague or anyone else.

As far as I'm concerned, I'm always ready to meet war crimes investigators. I admire most of those I have met. And if we ever have an international court to try all the villains, I might change my mind. But until then, a reporter's job does not include joining the prosecution. We are witnesses and we write our testimony and we name, if we can, the bad guys. Then it is for the world to act. Not us.

Fergal Keane is away