The Bulldogs have won a NSW Supreme Court injunction blocking runaway NRL star Sonny Bill Williams from playing rugby union in France.

The court win for the Bulldogs and the NRL means Williams will be in contempt of court if he proceeds to play in a friendly match for Toulon, which kicks off early Saturday morning Sydney time (0230 AEST).

The injunction was granted in Sydney on Friday despite the fact Williams was not represented.

Earlier this week, he was served court documents informing him of the hearing after a process server spotted him at a training session in Toulon.

"The evidence before the court satisfies that the first defendant (Williams) has failed to attend to his contractual responsibilities," Justice Robert Austin told the parties.

"There is evidence he has entered into a contract with the second defendant (Toulon) ... and intends to play in a rugby match this evening."

Justice Austin said he had considered the jurisdictional difficulties involved, given that Williams intends to remain in France.

But he acknowledged the plaintiffs - the Bulldogs and the NRL - had proven Williams could be successfully sued for damages in NSW if he breached the order.

"My conclusion is that the making of an interlocutory interim injunction will not be futile."

Williams, 23, left Australia without warning almost two weeks ago, just one year into his five-year deal with the Bulldogs.

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