Whether true or not, the idea that Yasser Arafat, the Palestinian leader who died rather mysteriously in 2004, had been deliberately poisoned continues to fascinate people. It's one of those stories that just won't go away – like the "murder" of Princess Diana and the various Kennedy assassination plots.

The Arafat conspiracy theorists were given a boost on Tuesday when Farouk Kaddoumi, secretary-general of Fatah's central committee, claimed to have minutes of a meeting in which two senior Palestinians – Mahmoud Abbas (who replaced Arafat as president) and security chief Mohammed Dahlan – supposedly sat down with the Israelis and Americans and discussed Arafat's impending murder.

Setting aside the question of whether this claim is credible, the fact that Kaddoumi made it this week in front of TV cameras is certainly news that should be reported. It's part of the cut and thrust of Palestinian politics. Kaddoumi is one of Fatah's awkward squad and there are many who believe he was trying to cause mischief ahead of next month's Fatah congress – the first for 20 years.

The reaction from Fatah's establishment has been entirely predictable. Instead of doing the sensible thing and challenging Kaddoumi to produce his evidence, they have banned al-Jazeera – one of several TV channels that broadcast his remarks – from operating in the West Bank. Apart from being an infringement of free speech, this can only reinforce the belief of conspiracy theorists that something is being covered up.

What we see here, though, is also part of a much wider Arab problem – of leaders who can't adjust to a new era of transparency in which their actions are liable to be scrutinised and questioned as never before. The banning of al-Jazeera in the West Bank is just one example over the last few days of rearguard actions by Arab governments against this loss of control.

On Tuesday it emerged that a virtually unknown amateur poet in Egypt had been sentenced to three years in jail for writing verses that "insulted" President Hosni Mubarak (one of the offending lines said: "You made people feel confused and lost").

Al-Jazeera has also been under fire in Yemen, where the authorities don't want its reporters covering the insurrection in the south. In the words of one member of parliament for the ruling party, said: "It runs stories which Yemen's enemies completely exploit, especially the secessionists who aim to deform Yemen's image abroad.''

Yemen's new press court, set up specially to try journalists, opened for business at the weekend, with 150 cases pending. The first to be tried is an editor who published a story about corruption in a government ministry.

The press court, as one Yemeni journalist pointed out, is modelled on the government's special court for dealing with suspected terrorists – "The charges are even the same, 'threatening the country's security and stability'."

The Palestinian information ministry adopted the usual line yesterday when it said the ban on al-Jazeera was intended to protect "Palestinian interests", ie those of the Fatah establishment.

In the days when there was only print and terrestrial TV, this idea that the media should be harnessed in the service of "the nation" (as defined by those in power) was fairly easy to maintain. "Licensing" of non-government newspapers and the general culture of deference kept a lid on things within the country, while "undesirable" material from outside could be stopped at the borders.

That began to break down with the arrival of new media that recognised no national boundaries: first satellite television – al-Jazeera, the most popular Arabic channel, started up in 1996 – and then the internet. Old attitudes persist, though. In Jordan, for instance, the main front-page "news" every single day is what the king did yesterday.

The Arab League has also sought to hold back the tide with its Satellite Broadcasting Charter. Issued last year, mainly at the instigation of Egypt and Saudi Arabia, it was widely viewed as a last-ditch attempt to assert control over the medium, and it will almost certainly fail.

Sooner or later, Arab leaders will have to recognise that they can no longer dictate what can or cannot be said in public. Increasingly, their actions and decisions will be held up to the light. This is not something that politicians relish anywhere, as seen in Britain when Gordon Brown decided to hold the Iraq war inquiry in private (before coming under pressure and having second thoughts). In some countries politicians manage to adapt, but for the current generation of Arab leaders the shock of the new media may prove just too much to bear.