UPDATE: Ron Williams is confident his success in bringing down taxpayer-funded school chaplaincy will not jeopardise hundreds of other government programs.

The Toowoomba father was bunkered down in his solicitor's Sydney office when the High Court handed down its unanimous judgment yesterday.

It found the funding to school chaplaincy was illegal and that legislation pushed through to negate the Court's 2012 ruling in favour of Mr Williams' challenge was not valid law.

There were fears the ruling could jeopardise hundreds of other government-funded programs, but Mr Williams believed that was unlikely.

"They pretty much narrowed it down to the chaplaincy program so I don't know if the bogeyman of all the other programs I've supposedly put in danger exists anymore. I can't be accused of starting a snowball that can't be stopped," he said.

Prime Minister Tony Abbott told a press conference the government still supported the program and would study the judgment in the hope of finding a way to continue the funding.

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Existing funding is likely to allow the program to continue until the end of the year.

However, the $245.3 million funding package to maintain the program for another five years will be pulled.

Scripture Union Queensland chief executive Peter James said he was confident the program would continue under a different funding model, an opinion Mr Williams did not share.

". . . The court has acknowledged federal funding can continue for chaplaincy through state/territory grants," Mr James said.

Mr Williams said yesterday's result was an "enormous relief" after a gruelling campaign.

"It's not so much a champagne celebration as an emotional one, and a celebration of all the wonderful people who have given me moral and financial support."

UPDATE 11.30AM: The High Court has ruled against the Federal Government's funding of the school chaplaincy program.

The judgment was delivered at 10am today in Canberra.

The court found the funding of the school chaplains program to be "unlawful".

It is the second time Toowoomba dad Ron Williams has successfully challenged the chaplaincy program's funding model.

The ruling may mean the Federal Government's $245.3 million funding to continue the program for another five years will be pulled.

"The Court held that, in their operation with respect to the challenged funding agreement and the challenged payments made under that agreement, none of the challenged provisions is a valid law of the Commonwealth," the High Court ruled.

"The provisions are not, in their relevant operation, supported by a head of legislative power under the Constitution... The making of the payments was therefore held to be unlawful."

The ruling that the government had illegally paid for the chaplaincy scheme without parliamentary authority has potentially threatened the funding of hundreds of other programs, though the full effect remains to be seen.

Read the High Court's judgment here (PDF).

TODAY 6AM: Toowoomba man Ron Williams will learn in just a few hours if his High Court challenge to school chaplaincy was successful.

The final judgment is due to be handed down at 10am today, one month after the four-day hearing ended.

It was the second time Mr Williams contested the legality of school chaplains being funded by government.

He won the previous case after a 10-month wait for a ruling. His success was short-lived - within six days new legislation was pushed through which effectively rendered the ruling void.

Labor Senator Louise Pratt threw her support behind Mr Williams' fight in parliament on Tuesday, despite Labor continuing chaplaincy's funding when it was in government.

"Regardless of the outcome, it is important to me to see this program stopped," she said.

"Any person giving counselling to our young people should have the proper qualifications, as recognised by organisations like the Psychological Association, and should not hold discriminatory views."