Supreme Court reaffirms Citizens United in Montana case
The US Supreme Court has reaffirmed a 2010 decision that changed how political campaigns can be financed.
In a five-to-four decision, they struck down a 100-year-old Montana law that limited corporate campaign spending.
Montana state leaders condemned the decision.
The 2010 ruling, known as Citizens United, allowed corporations, labour organisations and wealthy donors to donate millions of dollars through groups known as super PACs.
Such groups can raise and spend unlimited money, but are not allowed to co-ordinate with the candidates they support.
Super PACs have already spent $133m (£85.5m) in political races this election cycle, spurred by a competitive primary season among Republican presidential candidates.'No serious doubt'
The ruling applies the 2010 decision to all state campaign finance law, saying that there was "no serious doubt" over whether Citizens United overruled the Montana law.
The decision was released without hearing full arguments in front of the court.
In the dissenting opinion, Justice Stephen Breyer argued that the case should be heard, because the state Supreme Court had found that spending by corporations "did in fact lead to corruption or the appearance of corruption in Montana".
In response to the ruling, Montana Governor Brian Schweitzer said the Supreme Court was endorsing "dirty, secret, corporate, foreign money".
Montana Attorney General Steve Bullock also called the US high court just "another political body".
Republican Senator Mitch McConnell called the court's decision on Monday "another important victory for freedom of speech, adding "the much predicted corporate tsunami that critics of Citizens United warned about simply did not occur".
Arizona Senator John McCain, a Republican who filed a "friend of the court" brief in support of Montana's law, told NBC News on Sunday the 2010 Citizens United ruling had been "arrogant, uninformed, naive".