The ACT opposition is warning that campaign laws passed in 2012 could be invalid, after a High Court of Australia ruling in December on NSW electoral laws.

The court overturned a ban on organisations and associations making donations to political parties in NSW after a constitutional challenge led by Unions NSW.

The court found the laws were invalid because they breached an implied freedom of communication.

The ACT Legislative Assembly is facing the prospect of redrafting its laws, which took two years to reform.

On Monday, Attorney-General Simon Corbell confirmed he had sought legal advice as to whether the ACT laws could be in breach of the constitution.

Opposition Leader Jeremy Hanson wrote to the government in January urging it to address the issue. On Monday, he said he feared the ACT legislation would be declared "inoperable" if it was challenged in the High Court.

The assembly passed the laws after a bitter debate in 2012, when then Greens leader Meredith Hunter called for political donations in the ACT to be restricted to individuals on the ACT electoral roll.

Caps on individual donations and on campaign expenditure by political parties and third-party campaigners were also introduced. "At the time Ms Hunter introduced the amendments, she expressly stated that her legislation was intended to implement the same restrictions then being considered in NSW on corporate or organisational donations," Mr Corbell said.

"Clearly, the territory now must consider whether the provisions of its own Electoral Act 1992 require significant amendment or repeal in light of the High Court's decision."

Mr Corbell said the High Court's decision "also touches on the territory's limits on total spending involving third parties".

Mr Hanson said the ACT government would have to move quickly and the assembly should review the laws at the same time that the ACT electoral commission was conducting its own assessment of the campaign finance reforms.

"I'd like this to be an open process but bitter experience has told me that this will be stitched up by Labor and the Greens behind closed doors to make sure they're getting what they want," he said.

Constitutional law expert George Williams said the ACT government would have real concerns about its law, but it remained valid "until somebody challenges it".

"It's wise for them to look at it and it may even be prudent to redraft the ACT's laws," Professor Williams said.

The High Court's decision caused an outcry in NSW, with Greens upper house MP John Kaye saying he feared it would enable corporations to "pour money into the coffers" of the Liberal and National parties.