The 9th U.S. Circuit Court of Appeals reinstated Montana's campaign donation limits, telling the federal judge who overturned it to outline his full reasoning so the panel can review the case.
The court intervened late Tuesday, less than a week after the judge's decision opened the door to unlimited money in state elections — during the height of election season.
Conservative groups emboldened by the 2010 U.S. Supreme Court's Citizens United decision have made Montana the center of the fight over many campaign finance restrictions.
The groups have convinced a federal judge to strike down several laws as unconstitutional, including the cap on contributions given to candidates by individuals and political parties.
Over the past week, Montana election officials had urged candidates to abide by the old limits. But attorneys for conservative and Republican groups advised candidates that they could take unlimited money during that window.
Some candidates said they would abide by the old limits, while others considered the idea of taking larger donations. The effect won't be known until disclosure reports are filed later with the state Commissioner of Political Practices.
The disclosure of donations is still required, although state officials worry that conservative groups will next attack that aspect of campaign finance law.
Montana has seen many of its laws struck down in the wake the Citizens United decision that opened the door for more corporate spending in federal races, citing freedom of speech issues.
Last month, a federal appeals court struck down Montana's ban on partisan endorsements of judicial candidates, citing Citizens United.
U.S. District Judge Charles Lovell earlier this year ruled as unconstitutional laws requiring attack ads to disclose voting records and a ban on knowingly false statements in such ads.
The Supreme Court also tossed the state's century-old, voter-approved ban on independent corporate political spending in state races.
That decision prompted a new ballot initiative that, if approved in November by voters, asks state leaders to seek a constitutional amendment undermining the high court's decision.