The NLRB enforces the National Labor Relations Act, which guarantees employees the right to organize and collectively bargain, or to refrain from doing so. Applicable Sections of the Act follow:
RIGHTS OF EMPLOYEES
Section 7: Employees shall have the right to self-organization, to form, join, or assist labor organizations, to bargain collectively through representatives of their own choosing, and to engage in other concerted activities for the purpose of collective bargaining or other mutual aid or protection, and shall also have the right to refrain from any or all such activities...
RIGHT TO STRIKE
Section 13: Nothing in this Act … shall be construed so as either to interfere with or impede or diminish in any way the right to strike or to affect the limitations or qualifications on that right.
UNFAIR LABOR PRACTICES (relevant sections)
Section 8(a)It shall be an unfair labor practice for an employer—
(1) to interfere with, restrain, or coerce employees in the exercise of the rights guaranteed in section 7;
(3) by discrimination in regard to hire or tenure of employment or any term or condition of employment to encourage or discourage membership in any labor organization
On the 8(a)(1) charge:
The U.S. Supreme Court delineated the line between protected employer speech versus unlawful employer speech under the NLRA in NLRB v. Gissel Packing Corp., 395 US 575, 618 (1969).
In General Electric Company, 215 NLRB 520 (1974), the National Labor Relations Board applied the Gissel test to set aside an election because the employer, citing concerns about possible future strikes, stated that the plant's nonunion status was a primary factor in choosing to locate a production line for a new motor there. In its decision, the Board distinguished an employer's right to take defensive action when threatened with an imminent strike from threats to transfer work "merely because of the possibility of a strike at some speculative future date."
Since then, the Board has repeatedly held that an employer violates section 8(a)(1) by threatening that employees will lose their jobs if they join a strike, or by predicting a loss of business and jobs because of unionization or strike disruptions without any factual basis. In contrast, the Board has found that employers may lawfully relate concerns raised by customers (Curwood, Inc., 339 NLRB 1137 (2003). They may also reference the possibility that unionization, including strikes, might harm relationships with consumers, as opposed to predicting “unavoidable consequences.”Miller Industries Towing Equipment, Inc., 342 NLRB 1074, 1075-76 (2004)
On the 8(a)(3) charge:
An employer’s discouragement of its employees’ participation in a legitimate strike constitutes discouragement of union membership within the meaning of this section. This applies to employer conduct designed to retaliate against employees for having engaged in a strike in the past (Capehorn Industry, 336 NLRB 364 (2001)where the employer failed to reinstate strikers when there was no legitimate business justification for permanently subcontracting the work), as well as employer conduct designed to forestall employees from exercising their right to strike in the future (Century Air Freight, 284 NLRB 730 (1987)where employer permanently subcontracted unit work and discharged employees in order to forestall the exercise of their right to strike; and Westpac Electric, 321 NLRB 1322 (1996), where employer isolated employee in retaliation for previous and anticipated future strike activities). In National Fabricators 295 NLRB 1095 (1989), where potential strikers were targeted for layoffs, the Board held that “disfavoring employees who were likely to strike, is the kind of coercive discrimination that…discourages…protected activity.”