Final answer:
The National Labor Relations Act (NLRA) prohibits employer domination of unions. The act supports collective bargaining and established the National Labor Relations Board (NLRB) to enforce labor laws and mediate disputes.
Step-by-step explanation:
The activity prohibited by the National Labor Relations Act (NLRA), or the Wagner Act, is employer domination of unions. The NLRA was established to protect the rights of workers and unions, including the right to collective bargaining. Specifically, the law prohibits several practices by employers such as the creation of company unions, or actions that would lead to the dominance over a labor organization. The acts that are illegal under the NLRA include employer interference, restraint or coercion directed at labor organizations, and yellow-dog contracts where employees agree as a condition of employment not to join a union.
Collective bargaining is actually a core component that the NLRA supports and encourages, as it's a process wherein employers and unions negotiate to determine the terms of employment. The Wagner Act also led to the creation of the National Labor Relations Board (NLRB) to enforce these rules and to act as a mediator in disputes between unions and employers.