The Wallaby fullback has made more controversial comments about homosexuals and the gender debate.
Yesterday Tasmania became the first Australian jurisdiction to make gender an option on birth certificates.
After the announcement, the Wallabies star took to Twitter to tell people to "turn away" from their evil ways after the announcement.
"The devil has blinded so many people in this world, REPENT and turn away from your evil ways. Turn to Jesus Christ who will set you free," Folau posted.
Rugby Australia released a statement shortly after saying the post was 'unacceptable'.
"Rugby Australia is aware of a post made by Israel Folau on his Instagram account this afternoon," Rugby Australia said in a statement.
"The content within the post is unacceptable. It does not represent the values of the sport and is disrespectful to members of the Rugby community.
"The Rugby Australia Integrity Unit has been engaged on the matter tonight."
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Sydney Morning Herald columnist Peter FitzSimons wrote that Folau's latest post should see Rugby Australia cut their ties with the 73-test Wallaby.
"Israel Folau has to go, and will go," the former Australian test player wrote.
"Quick. Clean. Gone. At least until such times as he repents.
"Rugby Australia simply has no choice. They cannot go through one more time the agony of last year when Folau's social media comments trumpeting that gays would go to hell, saw rugby lose sponsors, fans and support," FitzSimons said in the Sydney Morning Herald.
According to rugby.com.au, there was a reported clause in Folau's contract negotiations last year that was specific to his use of social media.
The tweet has been widely shared and commented on, with most people responding having a negative view of his comments."Why would Jesus have wanted more detail in birth records? How is that possibly connected to his faith, or the religion of his followers?" one user asked.
"Folau needs a social media team to do all his posts for him, you're extremely religious we get that but might be best to stay out of subjects that could easily offend in today's world," said another.
Retired England prop Joe Marler simply responded with an image of two men kissing.
However, others have come out in Folau's defence.
"Load of nonsense isn't it? They are confusing kids so much these days with all these gender nonsense," one man wrote.
Meanwhile, on Instagram, the Waratahs Super Rugby star warned sinners would be going to hell unless they repented.
The image he posted reads "warning" in bold, before listing "drunks, homosexuals, adulterers, liars, fornicators, thieves, atheists, idolaters, hell awaits you".
The former league and AFL player, now a rugby union star, created tension on social media last year for his stance on homosexuality.
Six months after tweeting his opposition to same-sex marriage, the Wallabies fullback posted on Instagram last April that gays would go to hell.
Rugby Australia CEO Raelene Castle said last year Folau was entitled to share his religious views but within limits.
"There's no doubt we've had conversations with Izzy about continuing to present his views in a respectful way. He is walking the line, we'll continue the dialogue with him," Castle told Fox Sports' Kick & Chase program in May 2018.
"On one hand you're dealing with a human rights issue and on the other hand you're dealing with freedom of speech and someone's right to express their views, whether it be religious or otherwise. I think the test continues to be whether that is done in a respectful way. That's the measure we'll continue to apply."
Folau, who is married to Silver Ferns shooter Maria Folau (nee Tutaia), made the comment in reply to a question on an image he posted on Instagram which showed "God's plan".
"@izzyfolau what was gods plan for gay people??" user Mike Sephton-Poultney asked. "HELL", Folau responded. "Unless they repent of their sins and turn to God."
Folau reinforced his comments after a meeting with Rugby Australia boss Raelene Castle last year, revealing he offered to walk away from the game.