Israel Folau has launched legal proceedings with the Fair Work Commission against Rugby Australia and the Waratahs.
Folau's lawyers said it was unlawful to terminate employment on the basis of religion under Section 772 of the Fair Work Act.
In a statement, Folau said: "No Australian of any faith should be fired for practising their religion."
The 30-year-old is seeking substantial remedies according to his lawyers.
The Australian Financial Review reported yesterday that the former Wallabies star hired commercial law firm Macpherson Kelley.
The firm's head of employment George Haros said they believe Rugby Australia acted "unlawfully".
"We believe Rugby Australia and the Waratahs have acted unfairly and unlawfully in their treatment of Israel," Haros told the AFR.
Haros will work closely with Melbourne-based silk Stuart Wood QC, a leading lawyer in unlawful termination cases where free speech is a central issue, the AFR reported.
The Fair Work Act protects employees from unlawful dismissal on religious grounds.
Folau decided not to appeal through Rugby Australia's internal channels, saying that he feared he would receive unfair treatment during the process.
"My decision not to commence Rugby Australia's appeal process is in no way an acceptance of the judicial panel's findings," Folau said in a statement.
"I simply do not have confidence in Rugby Australia's ability to treat me fairly or lawfully throughout this process."
More to come