A speech by Australian judge Patrick Keane KC has been met by a vociferous protest over his continued presence on the bench of Hong Kong’s controversial court of final appeal.

A slew of foreign judges has quit the court, with one arguing the rule of law in Hong Kong has been “profoundly compromised” and that the city-state is “becoming a totalitarian state”.

Of the six remaining foreign judges – down from 15 – four are Australian. Only two, including Keane, joined the court since the implementation of Hong Kong’s national security law, which criminalises acts of dissent and subversion, and is seen as a political weapon against the pro-democracy movement.

Keane spoke at Sydney’s Banco Court on Tuesday night, giving an address titled Christian Inspiration and Constitutional Insights that included quotes from such varied figures as Frederick the Great, Thomas Jefferson, John Locke and British judge Lord Jonathan Sumption, one of his former colleagues on the Hong Kong court bench.

Sumption quit the bench in June this year, writing in an excoriating opinion piece that the rule of law in Hong Kong was “profoundly compromised”, and that the territory was “becoming a totalitarian state”.

Sumption wrote that local judges were working under an “impossible political environment created by China”.

“I remained on the [court] in the hope that the presence of overseas judges would help sustain the rule of law. I fear that this is no longer realistic,” he wrote.

On Tuesday evening, on the forecourt of Sydney’s law courts building, protesters gathered bearing pictures of jailed Hong Kong pro-democracy publisher Jimmy Lai, who is being held in solitary confinement on charges – internationally seen as politically motivated – of organising illegal protests.

The Sydney protest seemingly prevented Keane from attending an advertised post-speech drinks. He had been due to attend but was not present.

Alerted to the protest, he left the court building via an alternative exit, as protesters held a flashing neon representation of Lai in chains, above the words “Prisoner of Conscience”.

One protester approached Keane in the street, filming him and asking: “Do you know Jimmy Lai?”

Keane declined to comment. The Guardian has sent a series of questions to Keane.

Keane, a justice of the Australian high court from 2013 until his retirement in 2022, has previously defended his position as a non-permanent judge on the Hong Kong bench.

He told the Guardian in 2023 “my own view would be that given how successful the court [of final appeal] has been in its role in upholding the rule of law, one should be very slow indeed to decline the opportunity to serve on such a successful court”.

He said the court had a long history as “a very successful institution that’s made an important contribution to the success of Hong Kong”, and that it was better to play a role rather than “vacate the field”.

“One has to be very careful about declining to do good work because one has an apprehension that one might be asked to do bad work,” he said.

But pro-democracy activists and Hong Kong advocacy groups have consistently called for foreign judges to quit the CFA bench, arguing their judicial credibility lends legitimacy to a legal system which has been undermined by the city’s worsening security environment, in particular the 2020 national security law.

Critics say the court cannot claim to stand fully independent of government wishes, and that the government wishes are increasingly anti-democratic. The court of final appeal is Hong Kong’s highest court, but on occasion the government has asked the Chinese central government – which has ultimate control of Hong Kong – to reinterpret laws after rulings it found unfavourable.

In November 2022 the Hong Kong government did precisely that after the CFA rejected its attempt to have foreign lawyers banned from representing clients in national security cases. Government prosecutors had been seeking to ban British lawyer Tim Owen from representing Lai in court. In December, Beijing’s top lawmaking body ruled that courts must get the Hong Kong leader’s approval to admit any foreign lawyer on a national security case.

Alyssa Fong, manager of the Committee for Freedom in Hong Kong Foundation, said it was “shocking” that Keane had chosen to join the bench after the implementation of the national security law, which saw mass arrests of pro-democracy demonstrators, and widespread repression of civil liberties and press freedoms.

“As a Hongkonger, it is heartbreaking,” she said.

Well-known figures from the international legal community sitting on the court lend legitimacy to the authoritarian crackdown in Hong Kong, she said.

“Following the string of resignations this summer, Justice Keane should reevaluate his position … and step down from the court of final appeal.”

Five foreign judges have resigned from the CFA this year, and 10 since the national security law was introduced. Several have cited the political situation in their reasons for leaving.

There are now just six foreign judges left: four Australians including Keane, and two from the UK. Keane and fellow Australian justice James Allsop are the only ones to have joined the bench since the national security law was introduced. British judge David Neuberger, who joined the court in 2009 and is hearing appeals from Lai, told the Guardian earlier this year that he still believed Hong Kong’s judiciary was independent, and its legal profession “thriving and able”.

The foreign judges are in the judiciary’s pool of non-permanent judges, who sit on the five-person bench hearing final appeals. The overseas judges typically come to the city on rotation, for about one month. They are flown to Hong Kong on an ad hoc basis determined by the chief justice, on first-class tickets and given luxury accommodation, as well as a reported payment of about HK$400,000 (£40,000, about A$77,000).