First, they arrest a woman for reciting the names of British troops killed in Iraq in an otherwise peaceful protest near the Cenotaph. Maya Evans, who had fallen foul of a clause in the Serious and Organised Crime and Police Act, was duly convicted last week, given a conditional discharge and left with a criminal record.

Then, an author taking part in a broadcast discussion about gay adoptions was telephoned by a policewoman and informed that her name had been noted following a complaint that she had made a "homophobic" remark on air. Lynette Burrows had offered her opinion that two homosexual men should not be allowed to adopt a boy, which is a view with which you may agree or disagree, but does not warrant a call from the local constabulary.

She was told that, although a crime had not been committed, it was policy to record details of such complaints, so Mrs Burrows is now, presumably, on some sinister register of people who express views that are not considered acceptable. Needless to say, she was flabbergasted to receive such a call. "This is a free country and we are entitled to express opinions on matters of public interest," she said.

But this is no longer true, though it is not the fault of the police. It is the fault of the Government for promoting laws that criminalise opinions judged unfashionable or objectionable, and of Parliament for passing them.

The police are often merely upholding an asinine measure that should never have been introduced in the first place. Ludicrously, they are - as in the case of the restrictions on demonstrations in the vicinity of Parliament - left to interpret the law as they see fit.

The measure under which Miss Evans was prosecuted (and there are another 20 or so cases pending) was inserted in a Bill whose main purpose was to establish a new FBI-style agency to tackle Mr Big criminals. The Government decided to use this legislation to create a security cordon around Westminster and framed the law in such a way that it would apply to individuals, and not just gatherings of people.

This was done to gag Brian Haw, the man whose long-standing vigil in Parliament Square has so irritated MPs. It soon transpired, however, that Mr Haw is the only person in the land immune from its impact, since the courts ruled it could not be made retrospective and, therefore, his protest continues.

However, because of the way the clause was drafted, anyone else who takes part in an unauthorised demonstration within one kilometre of the Palace of Westminster can now be prosecuted, even if they are simply standing on their own, neither posing a threat nor inconveniencing anybody else.

The justification given for this extraordinary measure is to protect MPs from possible threats to their security and to ensure they are able to go, unhindered, about their daily business of passing increasingly outlandish legislation.

Yet the area covered by these restrictions is so extensive that a nurse protesting against pay and conditions outside St Thomas Hospital on the other bank of the Thames would be breaking the law unless authority had been obtained in advance from the police.

The Act deliberately does not define what is meant by a demonstration - so a judgment of whether one is taking place is left entirely to a constable.

In the case of Miss Evans, an officer decided that ringing a bell and reciting a list of names constituted a protest for which an arrest could be made because prior authority had not been sought.

How could Parliament pass such a law, when it is so patently inimical to the freedom of speech that this country once considered fundamental? Why did MPs, who are meant to be the custodians of our values, let it happen?

Although the general principle behind the new law was contained in the Serious and Organised Crime and Police Act, the actual order that put it into effect was passed using delegated powers by a special standing committee, which is stacked in the Government's favour so that it can get its legislation through.

When the committee debated the measure in October, serious concerns were voiced on all sides, but Paul Goggins, the Home Office minister, saw nothing wrong. He said: "We value the importance of demonstrations. In a democracy, we have a right to be able to demonstrate our opinions and our views… I therefore make it absolutely plain that that is my belief and that is the view of the Government, and nothing in the order changes any of that."

But it quite clearly does; and it is absurd that the police have been left to define what is meant by a demonstration, a worrying trend that is to continue when the Government gives the police the power to dispense summary justice in certain circumstances.

Mr Goggins said constables would exercise their good sense and only acts that a "reasonable person" would regard as a demonstration would fall foul of the law. So, what definition could Mr Goggins offer? "The whole point of a demonstration is to convey a point of view," he said. "Someone demonstrates their point of view; that is a demonstration. It can be an individual person who so arranges their demonstration that they make their point."

By this measure, any expression of an opinion close to the Houses of Parliament - including, presumably, one laudatory of Tony Blair, not just critical - is to be considered a demonstration and, therefore, an arrestable offence if prior authority has not been obtained from the police.

Had Mrs Burrows made her remark in Parliament Square, rather than in a radio studio, she might have received more than just an offensive ticking-off from the local thought police.

Let us give the Government the benefit of the doubt and assume that the way this law is being applied was not its intention. In which case, we look forward to its immediate repeal.