Sacked rugby international Israel Folau believes he has a mission to "spread the word of God", according to his statement of claim calling for his reinstatement by Rugby Australia.

Key points: Israel Folau has called for his job back from Rugby Australia, labelling his dismissal "unreasonable restraint of trade"

Israel Folau has called for his job back from Rugby Australia, labelling his dismissal "unreasonable restraint of trade" The sacked Wallaby's claims were lodged by lawyers in the Federal Circuit Court

The sacked Wallaby's claims were lodged by lawyers in the Federal Circuit Court The statement comes as Folau sues Rubgy Australia and the NSW Waratahs for potentially millions in compensation

The "born again" Christian is suing Rugby Australia and Rugby NSW in the Federal Circuit Court, arguing unlawful termination of his $5.7 million contract on the grounds of religious discrimination and restraint of trade.

The statement of claim says Folau was baptised in December 2017 and is a devout and founding member of the Truth of Jesus Christ Church.

"Mr Folau believes that he has a mission and duty to spread what he believes to be the word of God, including messages contained within the Bible, and doctrine from his faith as preached by the Truth of Jesus Christ Church," the claim states.

"Mr Folau's religious beliefs go to the very essence of his personhood and define him as a human being."

His contract was ripped up after he posted on Instagram in April that homosexuals, amongst others, would go to hell.

It comes as the Wallabies prepare for the Rugby World Cup in Japan next month without the 74-Test veteran and fourth-highest try-scorer in Australian rugby history.

'No way' Folau will get job back, expert says

In his 26-page statement of claim, apart from demanding his job back, Folau is also demanding an apology from Rugby Australia and Rugby NSW and compensation, which was previously claimed to be worth around $5 million.

But Sydney University lecturer in employment law Giuseppe Carabetta said "there's absolutely no way he's getting his job back".

He said the statement of claim was about setting the groundwork for an eventual settlement.

Folau's lawyers said his sacking was an "unreasonable restraint of trade". ( AAP: Dave Hunt )

"They're going to give him money if he's successful," Mr Carabetta said.

The statement of claim sets out the legal arguments Folau's team will use when the case resumes in December.

It rests on the professional players' code of conduct, which Rugby Australia claims Folau breached with his Instagram post.

"They [Rugby Australia] will argue that they're acting on the breach of the code," Mr Carabetta said.

He said Folau's lawyers would argue that does not apply if the code is invalid.

Folau's social media helped spread 'the word of God'

The statement of claim said Folau used his social media posts almost exclusively to post content that "represented the word of God", and that they were written in his own time.

Folau has claimed he is not homophobic or bigoted.

In 2014, he appeared on the cover of the LGBTI publication, the Star Observer, and he supported the Bingham Cup, an international gay rugby competition, it said.

His lawyers claim that if his contract prohibited Folau from expressing his religious beliefs in his own time, it was against public policy and therefore "void at law".

For that reason, they argue his social media posts were not a breach of the code of conduct.

Mr Carabetta said, "even if the code is valid, Folau will argue he has not breached it, because there's nothing in his acts that are offensive".

The claim attempts to turn the tables on Rugby Australia, by claiming it was the governing body that breached Folau's contract.

It claims Rugby Australia acted in contravention of the Laws of World Rugby which says unions (including Rugby Australia) cannot discriminate, offend, insult or humiliate anyone on the grounds of their religion.

The claim also states that Folau's termination was a restraint of trade because it prevented him from playing rugby union at an international level.

Mr Carabetta said the case was testing new ground.

"I've never seen this before. It's the first time, we've never had a decision on religion under the unlawful termination provisions," he said.

The case is due for a mediation hearing in December.

If that is unsuccessful — as expected — a trial will be held next year.