'Africa is giving nothing to anyone – apart from Aids." A nasty remark, and untrue.

Africa gives us many things, including most of the world's gold and diamonds, and you can't blame a country for the spread of sexually transmitted diseases. Nevertheless, I'm not sure I would say that this remark, from the Irish journalist and commentator, Kevin Myers, in the Irish Independent in 2008 should actually be censored. But be in no doubt – it cannot be said again in Ireland. And nor can anything like it.

This was one of the earliest cases taken to the Press Council of Ireland (PCI), the system of press regulation Alex Salmond would like to see in Scotland. It was referred to the Irish press watchdog by the Immigrant Council of Ireland, and a number of non-governmental organisations, on the grounds that it breached four of the principles of the council's code of practice for journalists: 1) accuracy, 2) fairness, 3) respect for rights and 8) incitement to hatred. The council accepted that it was "gratuitously offensive", and "was likely to cause grave offence to people throughout sub-Saharan Africa". It ruled that the article "did breach principle 8 of the code". Though confusingly, it did not conclude that it was "likely to stir up hatred".

But the matter didn't end there. After the ruling, in 2009, the Irish Times ran a headline: "Press Council upholds complaint against Myers article." Myers then took the Irish Times to the Press Council on the grounds that this breached principles 1) accuracy, 3) fairness and 4) respect for rights. The Times argued that its headline was accurate and fair since it was a direct quote from the Press Council itself. But the Press Council didn't agree and said that even though this is what it had said, the Irish Times headline was misleading and it "breached principle 1 of the Code". However, just to make things even more confusing, it only partially upheld the complaint made by Myers against the Irish Times.

I'm afraid this is what happens when you put a group of lawyers, ex-judges and professors in charge of regulating the press. The PCI tried to apply these very broad and subjective criteria, like offensive and fair, to a piece of journalism that was neither. But they also realised that freedom of speech does require that sometimes offensive and unfair things are said. So, they tried to have it both ways – they upheld the complaint, and didn't uphold it at the same time.

But this has had one very clear outcome: censorship. The PCI may only have partially upheld the complaint against Mr Myers, but that means that the sentence used cannot be printed in any Irish publication ever again.

The PCI model is hailed as the best around by many politicians seeking to address the phone-hacking scandal. It is independent, it has statutory underpinning, it is not under the control of government – at least not directly. But slowly and surely it is closing down spirited commentary and restricting freedom of speech.

The proposals from the Scottish expert panel under Lord McCluskey on implementing the Leveson Commission here are more draconian, in that there is a direct political involvement through the appointment, by Government ministers, of a "recognition commissioner" – a figure who would oversee any regulation body set up by the press.

The Leveson report proposed that the ultimate oversight would come from media regulators Ofcom. McCluskey has also ditched Leveson's proposal that it should only be the printed press that is regulated, and has included "all significant news publishers" in whatever published form, including the internet, blogs, tweets – the lot. He has also rejected Leveson's proposal that publications should be able to opt in and opt out of the press regulatory regime. Under McCluskey's law, statutory regulation would be compulsory and it would be universal – like the law of contempt or the harassment laws.

There is logic to McCluskey's proposals. One of the anomalies of Leveson was that he only focused on the press, meaning that if you read this article in print it would be regulated, but if you read it online it would not. But the impact is regulation, which I am afraid will lead to draconian restrictions being placed on freedom of speech. As soon as you get a committee of the great and the good applying vague standards and codes of practice, you are likely to get a spiral of precedents that will strangle free expression.

Few liberals cared much about Kevin Myers, since he was a right-winger, but wait until someone who says that Israel is killing innocent people in Gaza is taken to the Press Council. George Galloway called Tony Blair a murderer – but he won't be able to say that in print or online. Some of the descriptions of Brian Souter, during the "Keep the Clause" campaign against the promotion of homosexuality in schools, would be actionable, as would many of the remarks made by his supporters. Feminists who say silly things like "all men are rapists" could be in the dock , as would loud-mouths like Ray Winstone who said he was "raped by taxes". Words and images will be weighed and calibrated on subjective scales of right and wrong and offensiveness.

Countless Private Eye covers would be actionable because humour is no defence. In June 2008 it ran a front page on the Zimbabwe elections with Robert Mugabe saying: "The opposition were soundly beaten", with another speech bubble adding: "To death". You might think it is not possible to be gratuitously offensive about Robert Mugabe, but the government of Zimbabwe might think differently. Private Eye may not even be on sale in Scotland if McCluskey's proposals are implemented because its editor, Ian Hislop, has already said he will not accept regulation.

But how do we stop journalists from phone hacking, blagging medical records, bribing police, stalking minors, harassing film actresses? Surely we need regulation. Yes – but that should be done by applying the existing law. All these offences, perpetrated by the gutter press, are already illegal. This is the point. The new Press Council, if it is on Irish lines, will end up trying to limit the power of the press to give offence to people. And that's where censorship begins.