Three groups filed papers with Justice Anthony Kennedy on Friday, saying that the Montana court's decision in December is out of step with Kennedy's majority opinion in the 2010 Citizens United case that struck down a federal ban on independent campaign spending.
The American Tradition Partnership and two other groups sued soon after the 2010 decision to overturn Montana's century-old corporate spending ban. But the state Supreme Court said the Montana law could remain in place because it was a response to political corruption and allows for some corporate spending.
Montana holds primary elections on June 5.
Copyright 2012 The Associated Press.
