(Courthouse News Service) – The Ninth Circuit on Wednesday declined to rehear a challenge of Montana’s campaign contribution law en banc, setting up a possible U.S. Supreme Court review.

In a legal tug of war that dates back to 2011, several Republican groups and individuals brought a lawsuit claiming Montana’s campaign funding caps were unconstitutional because it limited their free speech rights.

This past October, a Ninth Circuit panel reinstated the campaign contribution limits, reversing a federal judge’s decision to permanently enjoin the state from enforcing the law. In its decision, the panel ruled the caps minimized the risk of corruption.

Wednesday’s decision not to rehear the case en banc spurred a written dissent by U.S. Circuit Judge Sandra Ikuta, which was joined by four other circuit judges. Ikuta wrote the majority failed to apply U.S. Supreme Court precedent regarding campaign spending limits.

“Our court may not ignore such an important change in Supreme Court jurisprudence,” Ikuta wrote, referencing the landmark Citizens United v. Federal Election Commission which bars government from limiting independent campaign expenditures by corporations and political action committees.

“In light of the Supreme Court’s clarification, a state can justify imposing regulations limiting individuals’ political speech (via limiting political contributions) only by producing evidence that it has a real problem in combating actual or apparent quid pro quo corruption,” Ikuta wrote in the dissent.

U.S. Circuit Judges Raymond Fisher and Mary Murguia, both part of the original panel, rebuffed those arguments in their response.

“The evidentiary standard established by the Supreme Court requires that a state need only demonstrate a risk of quid pro quo corruption or its appearance that is neither conjectural nor illusory,” they wrote. “That is the standard we correctly applied here.”

They criticized the dissent, arguing those in favor of en banc rehearing could reference no decision or law that required the state to prove corruption in order to justify campaign contribution caps.

“Tellingly, the dissent can cite to no authority, at either the Supreme Court or any other level, requiring a state to prove the existence of quid pro quo arrangements at step one,” Fisher and Murguia wrote. “The Supreme Court has never required a state to do so. Instead, the Court has required a state to demonstrate only ‘a cognizable risk of corruption’ – a ‘risk of quid pro quo corruption or its appearance’ that rises above ‘mere conjecture.’”

Montana will hold primary elections on June 5. Under the state law, donors can give up to $180 to candidates running in state races. Under federal limits, U.S. House and Senate candidates are limited to $2,700.

The office of Montana Attorney General Tim Fox did not immediately respond to an email for comment.