WASHINGTON (AP) – The Supreme Court on Monday reaffirmed its 2-year-old decision allowing corporations to spend freely to influence elections. The justices struck down a Montana law limiting corporate campaign spending.

By a 5-4 vote, the court’s conservative justices said the decision in the Citizens United case in 2010 applies to state campaign finance laws and guarantees corporate and labor union interests the right to spend freely to advocate for or against candidates for state and local offices.

The majority turned away pleas from the court’s liberal justices to give a full hearing to the case because massive campaign spending since the January 2010 ruling has called into question some of its underpinnings.

The same five justices said in 2010 that corporations have a constitutional right to be heard in election campaigns. The decision paved the way for unlimited spending by corporations and labor unions in elections for Congress and the president, as long as the dollars are independent of the campaigns they are intended to help. The decision, grounded in the freedom of speech, appeared to apply equally to state contests.

But Montana aggressively defended its 1912 law against a challenge from corporations seeking to be free of spending limits, and the state Supreme Court sided with the state.