Bulldogs chief executive Todd Greenberg says the club will take out an injunction to prevent Sonny Bill Williams from playing elsewhere after the star back-rower reportedly flew to France to take up a $3 million rugby union offer.

Williams stunned the rugby league fraternity by walking out on the Bulldogs, and is understood to be linking up with second division rugby club Toulon on a lucrative two-year deal.

Greenberg said Williams's manager Khoder Nasser had confirmed his client had left the country but the `Dogs boss said he had no intention of letting the 22-year-old take-up the deal.

"Quite simply, if Sonny intends to play overseas, we'll be looking to take out an injunction which will effectively stop him playing in France, England or anywhere else he intends to do it," Greenberg said.

Asked whether the issue was likely to end up in the courts, Greenberg said: "I suggest at this early stage that you are probably right but we are going to have to review all our options to make sure that the Bulldogs are well covered.

"I've had QCs look at his contract and there is absolutely no get-out clause.

"I'm shocked that he's left because I saw him Oatley at 7.30am this morning.

Williams had been chosen in the Bulldogs team to play the Dragons on Monday night in Sydney.

NRL chief executive David Gallop, who will hold a special press conference at midday on Sunday to address the issue, said he was disappointed with Williams's decision.

"It is unacceptable to walk out on a contract," he said.

"If Sonny Bill Williams has personal issues, we will be happy to discuss them with him but we will support the Bulldogs in enforcing their contract and that includes preventing him from playing other than under that contract.

"Certainly the club, his teammates and the fans are entitled to some explanation for what has happened."

Bulldogs greats were unanimous in admonishing Williams' walk-out, with ex-chief executive Steve Mortimer claiming the Kiwi had let down a club which had gone out of its way to accommodate him.

"I'm absolutely bewildered after what this club has done for Sonny," Mortimer said.

"But I'm sure there's more to this than what's out there."

Former premiership-winning lock Paul Langmack claimed it wasn't just the Bulldogs who had been let down.

"It's unbelievable. It's not just what he's done to the club, it's what he's done to the game," Langmack said.

"I'm in shock. Canterbury have bent over backwards for him. It's a problem for the game that blokes think they can just pack up and walk out."

The New Zealand Test star had been signed to the Bulldogs until 2012 for an estimated $450,000 a year.

But he's been at loggerheads with the club for sometime, claiming he's worth more money.

Williams was also upset with what he perceives as excessive media scrutiny into his private life and at the Bulldogs making him publicly admit he had problems with alcohol last year.

His departure comes after St George Illawarra centre Mark Gasnier also signed a deal with French rugby club Stade Francais worth an estimated $2 million over two years.

Toulon are currently in the second division of French rugby but have been promoted to the top flight for next season.

Meanwhile, Toulon denied they had signed Williams.

Mourad Boudjellal, Toulon's president, told AFP that Williams and the club had spoken a while ago but there was no deal.

"We did make contact some time ago with Sonny Bill Williams," Boudjellal told AFP from Miami.

"He said to us that he wanted to move from rugby league to union but that is where it finished.

"I cannot confirm what was on Canterbury's website. However, I deny that it is true."

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