The justices ruled in an unsigned opinion that Montana's law was in conflict with the court's 2010 Citizens United decision, which shifted the campaign finance landscape, opening the door to the massive political expenditures that have been shaping this year's presidential race. The decision was 5-4, split along ideological lines.
Despite the Citizens United decision, the Montana Supreme Court had refused to strike down the state's ban on election spending by corporations. Its judges cited Montana's history of "copper kings" who bribed legislators. Advocates of campaign finance reform had hoped that the current wave of election-related spending would help make their case for the need to reconsider Citizens United.
Still, it was considered highly unlikely that the court, in its current configuration, would reverse itself on such a recent ruling.
The court issued a summary reversal without waiting to hear oral arguments in the case.
In a dissent, Justice Stephen Breyer wrote that "Montana's experience, like considerable experience elsewhere since the Court’s decision in Citizens United, casts grave doubts on the Court’s supposition that independent expenditures do not corrupt or appear to do so." But he acknowledged that the court was not likely to reconsider the ruling.
Advocates for stricter campaign finance regulations said they would continue their fight for tougher laws in Congress and the courts.
"Citizens and the nation are not going to accept the Supreme Court-imposed campaign finance system that allows our government to be auctioned off to billionaires, millionaires, corporate funders and other special interests using political money to buy influence and results," said Fred Wertheimer, president of Democracy 21. "A major national campaign finance reform movement will begin immediately after the 2012 elections."