The ban was announced on Thursday after a meeting of the NRL's disciplinary committee in Paris.
The ban could be reduced to 30 days if Chabal agrees to carry out "activities in the general interest", including helping with the development of young players.
The ban comes into effect immediately, even though Chabal has already served a two-week ban imposed by his club Racing-Metro since describing Top 14 referees as "useless" in an interview.
That means that Chabal will miss the Top 14 play-offs, in which Racing are due to play either Castres or Montpellier in Marseille on May 28.
On Wednesday, France coach Marc Lievremont left the 33-year-old Chabal out of his World Cup squad, saying his decision to do so was based entirely on performance.
"I have assured Sebastien that I judged him only on sporting reasons and that the controversy had nothing to do with my choice," he said.
"The choice was not easy because Sebastien Chabal is important in the squad, but I have chosen to rely on younger players to help the squad keep progressing."
However, Racing coach Pierre Berbizier said he believed Chabal was being punished.
"I am surprised and sad for Sebastien," he said of his omission.
"He has paid for his comments about referees. He is the victim, not of sporting performances, but of the parasites that surround him and prevent him from concentrating solely on rugby."
Gilbert has released a new line of rugby cleats. The Gilbert Virtuo 8S is part of the exciting new product. Check it out.
The Barbarians are one of the top invitational rugby sides with a long history and classic rugby jersey.
The Nike Tiempo is a solid rugby cleat and one of few styles still made from full-grain natural leather.
The Lions get ready for their matches with this green training jersey. It's what the players wear. Get in the Gear!
A cool looking all black rugby cleat with the high performance adidas is known for. Get in the Gear!
Wear the crest of the British and Irish Lions on your t-shirt. A great look for the summer.
The Lions are ready to get their Australia tour underway. They arrive in Perth on Monday.
The New Zealand All Blacks training jersey for 2013/14. Get in the Gear!
The USA Rugby Pro Alternate rugby jersey is perfect for any fan of the Eagles. Get yours to wear during the summer Test matches.
The NEW All Blacks 2013/14 jersey has arrived at World Rugby Shop. Dare to wear the colors of the All Blacks.