Pauline Hanson could potentially succeed in having a key plank of the Racial Discrimination Act declared unconstitutional if she launches a High Court challenge, legal experts say.

The One Nation leader last month lost an appeal in the Federal Court against an earlier ruling in 2024 that found she had breached Section 18C of the Racial Discrimination Act with a 2022 tweet telling Greens Senator Mehreen Faruqi to “pack your bags and piss off back to Pakistan” after she declared she could not “mourn the leader of a racist empire built on stolen lives, land and wealth of colonised peoples” following the Queen’s death.

Louise Clegg, a former barrister and the wife of Opposition Leader Angus Taylor, is arguing the law is unconstitutional.

The Samuel Griffith Society, a constitutionally conservative group in favour of retaining the British monarch as Australia’s head of state, argues the law from 1995 — making it illegal to “offend, insult, humiliate or intimidate” an individual or a group of people based on their race — could potentially be unconstitutional because it infringes on the implied right of political communication in the Constitution.

“It was a political debate — you had two senators who were both making political statements and that fact that we’re now censoring certain political statements whilst letting others through the gate, that’s the concern,” the group’s executive director Mia Schlicht told The Nightly.

The Federal Court judgment was also hugely subjective, favouring the opinion of Senator Faruqi over Senator Hanson, she argued.

“It acknowledged that Section 18C is not viewpoint neutral and therefore they’ve determined that Section 18C can prohibit one side of a political argument while leaving the opposing view unaffected,” Ms Schlicht said.

Last month’s Federal Court judgment upheld Justice Angus Stewart’s 2024 ruling that argued Senator Faruqi’s “characterisation of the British Empire as a ‘racist empire built on stolen lives, land and wealth of colonised peoples’ was not an expression of some fringe or revisionist historiography”.

Ms Schlict said that reflected a subjective, political judgment by the judges.

“I would also think that many people would find Faruqi’s statements pretty offensive — instead we have a court who literally wrote in the judgment that this was not a fringe view of Australia,” she said.

“The problem is that we’ve got judges who get to make those assessments about what is a fringe and what is a mainstream opinion which judges are in no place to make those policy assessments.”

Federal Court justices Melissa Perry, Geoffrey Kennett and Elizabeth Bennett’s July decision admitted Section 18C of the Racial Discrimination Act “casts a net”.

“It does not limit its coverage to hate speech or to acts that actually cause (or are intended to cause) insult, offence, humiliation or intimidation,” their judgement said.

“Further, while ‘insult’ has been held to involve more than ‘mere slights’, it is nevertheless a broad expression that sets a relatively low bar for the imposition of liability.

“The same point may be made about ‘offend’.”

Both Ms Clegg and University of Sydney constitutional law expert Professor Anne Twomey have also expressed concerns about Section 18C of the Racial Discrimination Act being potentially unconstitutional.

“If the implied freedom cannot robustly protect political communication on one of the defining issues that representative government now faces, it risks becoming less a constitutional protection than a technocratic constitutional curiosity for legal elites,” Ms Clegg wrote in an opinion for The Spectator magazine.

“After waiting more than 30 years the High Court may soon have the chance to show us whether the implied freedom of political communication in the Constitution is the real deal.”

Both are appearing at The Samuel Griffith Society’s annual conference in Sydney on August 22, a day after former Liberal prime minister John Howard addresses their annual dinner.

Paul Keating’s Labor government added Section 18C to the 1975 Racial Discrimination Act in 1995.

Former Liberal prime minister Tony Abbott’s government in August 2014 dumped plans to repeal Section 18C which in 2016 saw cartoonist Bill Leak hauled before the Australian Human Rights Commission over an illustration depicting an Aboriginal police officer and an Aboriginal deadbeat dad in a remote community. He died less than a year later.