Mark Spencer is PPS to Elizabeth Truss, the Environment Secretary, and thus himself a member of the Government.  Last year, he wrote to a constituent that the Government’s proposed Extremism Disruption Orders would in some circumstances “apply to a situation where a teacher was specifically teaching that gay marriage is wrong”.  He has also written that “racists, religious fundamentalists and homophobes” should not have “the freedom to spread their message of hate through what are often vulnerable communities”.

All this raises formidable questions. Is the UKIP member who seeks to adopt a child in Rotherham a racist?  Is the Catholic teacher who tells her pupils the church’s view of marriage a homophobe? Is the Sunni or Shi’ite who believes that Mohammed flew to heaven on a horse a religious fundamentalist?

I ask them because of the trailing in today’s papers of the Extremism Bill which will be part of this week’s Queen’s Speech.  The Sunday Telegraph report makes no specific mention of those Extremism Disruption Orders (EDOs) or of Extremism Banning Orders (EBOs) being contained within it.  But it does say that there will be “sweeping new laws [to] ban hate speakers from working with children and other vulnerable groups, in the same way that paedophiles are vetted to stop them being given jobs in schools”.

People with “clear links to extremism” would be required to be registered with the Disclosuure and Barring Service, the successor to the Criminal Records Bureau system, and employers would check with the DBS when candidates apply for jobs working with children, teenagers, or other vulnerable people. Records of people with connections to extremism will be disclosed to education officials, councils, and other employers.  The Bill could also ban organisations that promote hatred, which sounds as though the Government may introduce those EBOs, but is not sure.

It may not be certain because of the difficulty of nailing down a definiton of extremism in the first place.  The Telegraph claims that the Bill has been delayed because the Home Office has struggled to produce a legally watertight definition.  “One definition, from the government’s counter-extremism strategy, focuses on “vocal or active opposition to fundamental British values,” it says.  But what is a “British value”?  Is supporting liberal democracy, for example, a “value”?

I think we can agree that it is.   But why is such support distinctly British?  Do not most Canadians support liberal democracy, or most Spaniards for that matter – or many Iranians, since that country has a progressive section among its middle class?   After all, Britain’s public culture is distinctive because of its institutions rather than because of “values”.  Ministers may be wrestling with these conundrums, since the Telegraph also reports that such a definition has been dropped because it was thought to be vulnerable to legal challenge.

Perhaps it might be recast to make opposition to Parliamentary democracy the test.  That would catch the Salafist extremists who yearn to replace it with an Islamist state.  But it might also have caught Ed Miliband’s father, who seems to have spent much of his academic career teaching his students that the road to Parliamentary democracy was a dead-end for socialism.  Are we sure that a workable definition of extremism exists?  What about the law of unexpected consequences?

I spent my last years at Westminster working with Michael Gove and Pauline Neville-Jones to ensure that a Conservative Government, were one returned, would target extremism as well as violent extremism – that public policy should “drain the swamp” before the crocodiles “reach the boat”, as the Justice Secretary once put it.  Disagreement about whether government should pursue such an aim divided the Party at a senior level – just as it did the then Labour Government, the security services, the police and what has been called “the deep state”.

David Cameron’s instincts were robust, he listened to sense, and he acted wisely.  Under the Coalition, policy toughened up.  Government stopped lending patronage, appearing on platforms with, and funding Muslim Brotherhood or Jamaat Islami fellow travellers.  It has been able to do that by using common sense and without changing the law.  The growing realisation that Islamist extremism has only a tangential connection with our foreign policy has sunk further home.  After all, what did the Charlie Hebdo murders or attacks on Belgium have to do with foreign policy?

Cameron has thus helped to change the culture for the better.  No wonder Sadiq Khan was so keen, in his campaign for the London Mayoralty, to distance himself from – and in some cases apologise for – aspects of his past words and conduct.  It is true that there is further action against Islamist extremists which might not be possible without legal changes – such as ensuring that University Vice-Chancellors pull their collective finger out, bar hate preachers and thus make campuses safer for, say, Jewish or gay students.

And it is tempting to wave away these pernickity arguments about definitions – saying, as an American judge once said about hardcore porn, that one knows extremism when one sees it.  But it doesn’t follow that because a definition is difficult it can therefore be brushed aside.  Making law means finding definitions.  Get them wrong and consequences follow – such as Extremism Bill itself being extreme.  Ministers’ aims are right, at least as far as can be seen, but their means may not be.  Backbenchers and others will want to put this Bill under the magnifying glass.