A CONSTITUTIONAL law expert believes the Federal Government's carbon tax could be successfully challenged in the High Court.
Bryan Pape, a practising barrister and former University of New England academic, was commissioned to provide an opinion on the carbon legislation by conservative think-tank the Institute of Public Affairs.
And his opinion will no doubt provide pause for the country's conservative state premiers.
Mr Pape, a former National Party office holder and independent Senate candidate at the 2010 election, argues the carbon tax, due to come into effect on July 1, could be challenged on a number of grounds.
He argues, among other things, that the Commonwealth cannot tax state property, which he argues carbon dioxide emissions constitutes, and; that the Commonwealth cannot introduce a carbon tax with its external affairs powers.
IPA climate change policy director Tim Wilson said the states had not done enough to halt the implementation of the controversial carbon pricing legislation.
"The IPA commissioned a legal opinion because state governments have sat on their hands and let the Gillard government introduce a tax that they could potentially stop," Mr Wilson said.
"There's still a chance state governments could make Julia Gillard an honest politician by stopping a carbon tax under a government she leads."
While the IPA is not releasing the full opinion, citing a "a possible legal challenge to the tax", it has furnished the premiers and attorneys-general of the conservative states of NSW, Queensland and Western Australia with a copy ahead of Friday's 13/4 Council of Australian Governments meeting in Canberra.
Mr Wilson said the triumvirate had the "best legal standing for a potential challenge".
"The IPA is also writing to government MPs in each of these states making them aware that their government can act," Mr Wilson said.
"It's time state governments stood up against the carbon tax."
This is not the first time Mr Pape has proven a thorn in the side of a Labor government.
In 2009 he unsuccessfully challenged the then Kevin Rudd-led government's stimulus package in the High Court.
A spokesman for Climate Change Minister Greg Combet said "the government is confident in the legislative basis of the Clean Energy Act".
Queensland Premier Campbell Newman, who opposes the carbon tax, said on TuesdayApr10 he was seeking legal advice on the subject and if someone came forward with a credible legal opinion he would pursue it.