Last week I expressed my strong concern that the prime minister had failed to comply with her constitutional obligation to appoint as lord chancellor someone who appeared qualified to defend the rule of law.

The response of the lord chancellor has rather increased my concerns. Sources close to Liz Truss are now, according to the Guardian, saying the attacks on her amount to thinly veiled misogyny. They claim that no one ever attacked the appointment of Chris Grayling or Michael Gove as a breach of the law which requires that the prime minister can only recommend someone for appointment if they appear qualified by experience. So the only explanation for the attack on Truss must be her gender, it is said. This defence of the rule of law has become a row about sexism.

This is wrong on the facts: Grayling’s appointment was attacked on exactly the same basis. In evidence to the House of Lords’ constitution committee on 22 October 2014, when Grayling was lord chancellor, I said: “I thought that the way he had absolutely no understanding of the fact that his role was a special role to protect [the rule of law] … It indicated to me … that the prime minister had failed to comply with the obligation placed upon him by section 2 of the act to appoint somebody to the job with special qualities that would suit him to performing the job.”

The way Grayling behaved as lord chancellor and the appalling inroads he made on the most basic protections the law provides, particularly to the poor and immigrants, show that having a staunch defender of the principles of the law really matters. You have to be willing to make yourself unpopular with your colleagues in defending politically lonely positions, and be effective in defending them rather than just be a middle-ranking cabinet minister hoping to catch the eye of Theresa May for promotion.

‘The appalling inroads Chris Grayling made on the most basic protections the law provides, particularly to the poor and immigrants, show that having a big defender of the principles of the law really matters.’ Photograph: Darren Staples/Reuters

The law – section 2 of the Constitutional Reform Act 2005 – says that a person cannot become lord chancellor unless he or she appears to May to be “qualified by experience”. This section is saying, loud and clear, that May can only appoint someone if it appears their experience demonstrates they can do the job. And the key element of the job which led to the inclusion of this provision was defending the rule of law.

The section identifies categories of experience the prime minster can take into account in satisfying herself that the candidate is qualified – experience as a practising lawyer, an MP, a minister, an academic lawyer or any other professional knowledge May considers relevant.

It is intended to make May focus on whether the new lord chancellor is up to the job, not just on the basis of an untestable judgment but on their experience. The lord chancellor doesn’t have to be a lawyer but they must have relevant experience. A court would, of course, have expected the section to have been drawn to May’s attention before she made the appointment. If she did not know of the requirement then Liz Truss’s appointment would be flawed.

The 2005 reforms were made on the assumption that protections were needed to ensure the lord chancellor remained a powerful defender of the rule of law within government. I do not know whether May was aware of the provision before she appointed Liz Truss.

Some attempts have been made to suggest that Truss is qualified by experience. Richard Harwood QC said: “She has been a minister for nearly four years, two of those in the cabinet. Her reputation from those previous roles in education and environment, food and rural affairs is as an effective minister, although particularly passionate about British cheeses. None of that suggests that she cannot defend the rule of law across government.”

It is clear from everyone who has considered section 2 that simply having been a minister is insufficient. It does not of itself demonstrate either an understanding of what defending the rule of law involves, or give the holder of the office sufficient authority or inclination to defend it effectively. Grayling demonstrates this point eloquently.

The lord chief justice referred to the fact that she had studied politics, philosophy and economics at Oxford, was a management accountant and had been deputy director of Reform, a thinktank.

The Lords constitution committee put the requirement of section 2 as follows: “Given the importance of the lord chancellor’s duty to uphold the rule of law, the lord chancellor should have a high rank in cabinet and sufficient authority and seniority among his or her ministerial colleagues … It is not necessary to be prescriptive: more important than age or lack of ambition is that the person appointed has a clear understanding of his or her duties in relation to the rule of law and a willingness to speak up for that principle in dealings with ministerial colleagues, including the prime minister.”

While any court looking at this would give May very wide leeway in deciding whether Truss was qualified by experience – a subjective judgment – they would expect there to be something on which May’s judgment could be made. As Harwood’s valiant attempt demonstrates, there is simply nothing there – an enthusiasm for British cheeses does not begin to fit the bill. He doesn’t even suggest that she is qualified for the job. Rather, he says you can’t say she isn’t. A lot more is expected than that.

It is clear from everyone who has considered section 2 that simply having been a minister is insufficient

May is the culprit here, and the consequence of her decision is that the law lacks an effective defender in government. It is brilliant that there is a female lord chancellor, and it would be so much more brilliant if the person appointed also satisfied the requirements of the law and was likely to be an effective defender of the rule of law.

There were women qualified by experience to do the job, such as Anna Soubry, who has demonstrated her independence and knowledge of law. She would have had the authority in cabinet for the job required. All the signs are that Liz Truss doesn’t, and the people who will suffer will as ever be the poor and the immigrants who won’t be able to rely on someone to ensure they get the protections of the law.