The philosopher Kathleen Stock faced such severe harassment at the University of Sussex that the police advised her to avoid entering campus without a bodyguard and to install CCTV at her home. But the physical intimidation, aimed at making it as difficult as possible for her to do the job from which students repeatedly called for her to be fired, endured until she was forced to quit her professorial position last year. The university failed to adequately support her. Yet her view that biological sex cannot be changed by feelings of identity is quite unexceptional.

Sadly, there are where behaviour designed to silence and intimidate academics has gone unchallenged by universities. These intimidatory tactics take various forms, including open letters demanding dismissal, vexatious complaints, petitions demanding retractions, smear campaigns, no platforming, threats to disrupt speaking engagements and following through on those threats if the event nevertheless goes ahead. The targets of these tactics are typically women who believe that sex matters and who have the courage to say so.

One possible defence of these kinds of tactics is to frame the attempt to silence as itself a form of free speech: what we call the ¡°heckler¡¯s veto¡±. Indeed, gender critical feminist academics who are subject to such tactics are often brushed off by university managers for precisely this reason. But this confuses the right to protest and criticise with a right to silence others. Speech that is merely intended to silence the speech of others, far from contributing to knowledge and learning, narrows the scope of the educational sphere. To frame attempts to silence as equally valued speech ignores the educational purpose of the university.

The is why we have framed a ¡°heckler¡¯s veto¡± to the Higher Education (Freedom of Speech) Bill that is likely to be passed into English law within the next few months. The first part of the amendment makes it clear that the general duty on universities to take reasonably practical steps to secure free speech within the law does not include securing lawful speech that has the purpose and effect of restricting another's right to speech or academic freedom. In other words, the main duty is ¡°switched off¡± for such speech. This does not go as far as requiring an institution to prevent such speech. Rather, it clarifies that the university will not be under a positive duty to support it.

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The threshold for switching off the duty is set relatively high. To be considered a heckler¡¯s veto, it would need to be shown that speech or conduct had both the purpose and effect of restricting another¡¯s lawful speech or academic freedom. Unlawful speech such as harassment, criminal offences or defamation would already be outside the scope of the general duty because they are unlawful.

The second part of the amendment is a proactive duty on universities to take steps to mitigate the effects of attempts to silence another¡¯s speech or infringe their academic freedom. It is important to note that this would not affect the right to peaceful protest, but it might entail extra stewarding of an event, for example, or robust private and public support for an academic, or providing security for an academic¡¯s classes or lectures.

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The duty would cover unlawful harassment and defamation, but also otherwise lawful speech?that does not cross the line ¨C from a technical perspective ¨C into harassment. This is helpful because universities are not currently liable for harassment by third parties against their employees. In terms of employment law, students are just customers. Yet harassment by a small minority of zealous students can have a baleful influence on the intellectual environment for both academics and other students.

The philosopher Karl Popper pointed out in his ¡°paradox of tolerance¡± that ¡°if we are not prepared to defend a tolerant society against the onslaught of the intolerant, then the tolerant will be destroyed, and tolerance with them¡±. The intolerant will not meet us on the level of rational argument, but will instead insist that no one should be allowed to listen to certain arguments. Universities must resist the onslaught of the intolerant, not least for the sake of those students who are thereby deprived of the opportunity of open discussion on a wide range of topics.

Universities have displayed a failure of leadership when faced with staff and student campaigns against some women academics. To tackle the current crisis of academic freedom, they need to recognise that bullying, harassment and defamation are central to the tactics used by gender identity activists. This amendment is intended to give managers clarity about where their duties lie ¨C and a shove in the direction of standing up to bullies.

James Murray is a senior associate at legal and advisory firm Taylor Vinters. is professor of sociology at UCL and head of research at the UCL .

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