Which Act established that employers cannot force employees into contracts to retain their jobs?

The Noris LaGuardia Act of 1932 is significant in labor history as it prohibits employers from forcing employees into contracts that require them to refrain from union activities and protect workers' rights to organize. This act aimed to limit the extent to which employers could interfere with the labor rights of workers, asserting the principle that employees should not be bound by agreements that condition their employment on abstaining from union membership or activities.

In the context of labor relations, this act established a legal framework that respects workers' rights, enabling them to join unions and engage in collective bargaining without the threat of coercive contracts imposed by their employers. This foundational legislation laid the groundwork for subsequent labor rights initiatives and reinforced employees' freedoms in the workplace.

The other options refer to different legislative measures that address various aspects of labor relations but do not specifically prohibit employers from imposing mandatory contracts related to job retention in the same way the Noris LaGuardia Act does.