Some Republican senators want to prohibit union-only work places, which they contend could deter some businesses from locating in Missouri.
Missouri businesses currently have the option of requiring union fees from employees.
That means it would bypass Democratic Gov. Jay Nixon.
Earlier this session, Sen. Luann Ridgeway, of Smithville, filed a right-to-work proposal that would require the governor's signature to become law. It would not go on the ballot.
The right-to-work issue last went before Missouri voters in 1978. It was overwhelmingly defeated.