Nearly half of US states have thrown their weight behind a legal defence of local laws restricting corporate money in politics by asking the supreme court to revisit its widely-criticised ban on similar national legislation.

The states filed a brief with the supreme court on Monday in support of a century-old law in Montana – the Corrupt Practices Act – against companies pumping money into elections.

The law was struck down by a Montana court following the US supreme court ruling two years ago in the Citizens United case, which lifted most restrictions on corporations spending money on political advertising. However, the Montana supreme court has since upheld the state law, putting it in conflict with the Citizens United ruling.

If the supreme court agrees to take up the case, it is not likely to overturn Citizens United, but it could hand down a decision that would give state legislatures greater leeway in limiting corporate money in politics.

The states argue that corporate money can have an even more corroding effect at a local level than on national politics.

The Montana supreme court ruled that the ban was justified because of a history in the state of powerful corporate interests, copper mining companies, distorting politics with money. The ban was passed by a referendum in 1912.

That position has been challenged by a conservative interest group, American Tradition Partnership, which has asked the US supreme court to overturn the Montana ruling. The court blocked its implementation in February and is now considering whether to hear arguments in the case or simply issue a ruling reversing the Montana judgement.

In a submission to the supreme court on Monday, attorneys general from 22 states and Washington, DC representing both major parties called for the Montana law to be upheld.

"The Montana law at issue here, like many other state laws regulating corporate campaign expenditures in state and local elections, is sharply different from the federal law struck down in Citizens United, and the Court need not revise its ruling in Citizens United in order to sustain the challenged Montana law," wrote New York's attorney-general, Eric Schneiderman, in the brief.

The challenge over the Montana action has been backed by Senator John McCain, who authored the campaign finance law struck down by the US supreme court in Citizens United. In that ruling, Justice Anthony Kennedy's majority opinion said that money does not "give rise to corruption or the appearance of corruption".

In his brief in the Montana case, McCain argued that there is already evidence since the Citizens United ruling that large sums of money thrown into the political process is having a corrupting effect.

"A problem does exist. Evidence from the 2010 and 2012 electoral cycles has demonstrated that so-called independent expenditures create a strong potential for corruption and the perception thereof. The news confirms, daily, that existing campaign finance rules purporting to provide for 'independence' and 'disclosure' in fact provide neither.

"Regulatory filings show that much of the funding for independent expenditures comes from shell companies, pass-through entities, and non-profit organizations that conceal the true source of the individuals and companies supporting them," said McCain's brief.

But ATP said in its petition to the supreme court said there is no evidence Citizens United has corrupted the political process and that Montana's history of past abuses has no bearing on the law today.

"Citizens United has not proven unworkable, as evidenced by those who have exercised their liberty under it. Lower courts, except for the decision below, have uniformly followed this court's holding, and legislatures and government agencies, with few exceptions, have implemented the protections of Citizens United," it said.

"Is this court going to limit the right of speakers to engage in core political speech because they spend huge sums in doing so? Or because the state they happen to be in had corruption problems, or a corporation employed a lot of people, over a century ago? Or because the same corporation owned a lot of newspapers in the state in the 1950s? Or because the state they happen to be in has few people, a tradition of low-cost elections, or considerable candidate-voter contact?"

Two of the supreme court justices, Ruth Bader Ginsburg and Stephen Breyer, have welcomed the opportunity to revisit the Citizens United case."Montana's experience, and experience elsewhere since this court's decision in Citizens United … make it exceedingly difficult to maintain that independent expenditures by corporations 'do not give rise to corruption or the appearance of corruption,'" Ginsburg wrote.

She added that a further supreme court hearing "will give the court an opportunity to consider whether, in light of the huge sums currently deployed to buy candidates' allegiance, Citizens United should continue to hold sway". © Guardian News and Media 2012

[Money in politics photo via Shuttershock]