Voters in Missouri on Tuesday overwhelmingly decided to strike down a "right-to-work" law barring the collection of fees from private-sector workers who choose not to become union members, a crucial victory for organized labor following a series of setbacks.

Missouri residents voted by a 2-to-1 ratio to defeat the state law, which Republican lawmakers approved last year but had been put on hold pending the ballot referendum. Unions say that because they are required to bargain on behalf of all workers, including non-members, those workers should contribute a fair share of the dues paid by members.

The vote marked the first time that a right-to-work law was struck down at the polls. Twenty-seven other states have adopted such laws, including five since 2012, and the Missouri vote was seen as an important chance for labor groups to stem the tide.