"This is a destructive ruling for Montana's citizen democracy, and disturbing for those of us who believe that democracy is not for sale and politics is about values and issues, not money," Bullock said in a statement. "In declaring our campaign contribution limits unconstitutional, a federal judge has effectively put Montana's elections up for auction to the highest bidder."
The limits that were struck down range from $630 for an individual contributing to a governor's race to $160 for a state House candidate. The amounts are adjusted each election cycle to account for inflation.
The law also limited aggregate donations from political parties. A candidate for governor, for instance, was limited to accepting a maximum of $22,600 from all political party committees.
Montana has seen many of its laws struck down in the wake the 2010 U.S. Supreme Court's Citizens United decision that opened the door for more corporate spending in federal races, citing freedom of speech issues.
The Supreme Court subsequently 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.
Last month, a federal appeals court struck down Montana's ban on partisan endorsements of judicial candidates, citing Citizens United.
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. Lovell also decided that Montana cannot ban corporations from making contributions to political committees that make independent expenditures — a similar issue to the one addressed in Citizens United.