Missouri union activists turned in more than 310,000 signatures Friday calling for a ballot referendum on whether the state should keep the right-to-work law it adopted this year. The action put the law, which was to take effect Aug. 28, on hold until the referendum is held.

The state legislature has discretion on when to set the vote, but it is expected to take place on the fall general election ballot when incumbent Sen. Claire McCaskill, a Democrat, will face re-election.

Right-to-work laws prohibit workers from being forced to join or otherwise support a union as a condition of employment. Unions hate the laws because they are associated with membership losses and depleted treasuries. Business groups and Republicans back the laws, arguing that the laws attract business to states.

Republican Gov. Eric Greitens signed the law in February, making Missouri one of six states to have adopted a version since 2012.

"Right-to-work is to me an evil entity and they are trying to shove it down our throats," said Alexis Staughter, a union activist at a rally Friday at the statehouse to deliver the signatures.

The state GOP said the union conned people into signing the petitions. "Union bosses and Big Labor groups are being dishonest with Missourians about right-to-work, and as a result, we are seeing thousands of people rescind their signature from these anti-right-to-work petitions," said Missouri Republican Party Chairman Todd Graves Friday.