The barrister who ran a successful union challenge to New South Wales legislation restricting political donations says the judgement has national ramifications.

Parts of the state's Electoral Funding Act banning donations from groups or associations, have been declared invalid by the High Court.

Unions NSW launched a challenge to the laws, arguing that donations are a form of political freedom and that a ban is unconstitutional.

The union challenge was supported by five unions, while the NSW Government was backed by the Commonwealth, Western Australia, Queensland and Victoria.

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In a unanimous decision, the High Court found the laws invalid because they burden the implied freedom of communication on governmental and political matters, contrary to the Commonwealth constitution.

Managing partner of Holding Redlich Ian Robertson, who ran the challenge on behalf of Unions NSW, says the case was not particularly about the Labor movement and the Labor Party.

"It is about the right of people to make political donations and therefore participate in the political process," Mr Robertson said.

"What it says is that no parliament of Australia, whether state or federal, can act in the way that the NSW parliament has acted in this particular legislation."

The court also found that changes to the act which lumped together political expenditure by a political party and any union affiliated with it were unconstitutional.

"In practice that [part of the legislation] only applies to unions in the ALP," Mr Robertson said.

"There are caps on political expenditure in NSW and the legislation seeks to lump [them] together as one expenditure and therefore limit the expenditure by the ALP and an affiliated union but not an unaffiliated union.

"The High Court has also unanimously rejected that and said there is simply no basis for doing that and it, like the ban on donations, is contrary to the implied right of political communication which is in the Australian Constitution."

Unions NSW spokesman Mark Morey says the ruling is a win for the unions.

"This was about ensuring that people had the right to put their money together to participate in the democratic and political processes... that's what the win is about," Mr Morey said.

O'Farrell Government to revisit electoral laws

Unions NSW is calling on the O'Farrell Government to set up a bipartisan commission to reform the electoral laws in the wake of the High Court decision.

Premier Barry O'Farrell says he will revisit the issue.

"Clearly I'm disappointed that whilst the High Court recognises the reason the changes were introduced was to deal with corruption issues around Labor and donations, that nevertheless it has struck out these provisions," Mr O'Farrell said.

"The Government will clearly now consider its options. We've already announced that we will be redrafting the major legislation for electoral funding over the course of the next year.

"But look, whether it's outlaw motorcycle gangs who are simply trying to thwart the intent of Parliament in cleaning up gun crime across Sydney or whether it's the Labor Party and their union mates trying to thwart our efforts to clean up corruption, we'll not be put off."

A separate challenge to Queensland legislation which demands a vote of members if a union want to donate $10,000 or more, is due to be heard by the High Court next year.