In San Diego Unions v. Garmon (1959) 359 U.S. 236 79 S. Ct. 773, 3 L. Ed. 2d 775], the United States Supreme Court established 'general guidelines' for determining the permissible scope of state regulation of activity touching upon labor-management relations, and held that when an activity is arguably prohibited or protected by section 7 or section 8 of the National Labor Relations Act as amended (NLRA) (29 U.S.C. 151 et seq.), the state courts must defer to the exclusive competence of the NLRB in order to avoid state interference with national labor policy. (359 U.S. at p. 245 3 L. Ed. 2d at p. 783].) Title 29 United States Code section 157 (referred to as section 7) provides: "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 . . . ." Title 29 United States Code section 158 (referred to as section 8) provides in subdivision (a)(1) that it shall be an unfair labor practice for an employer "to interfere with, restrain, or coerce employees in the exercise of the rights guaranteed in section 157 of this title." The NLRA defines employees as not including any individual employed as a supervisor. (29 U.S.C. 152(3); see Balog v. LRJV, Inc. (1988) 204 Cal. App. 3d 1295, 1302 250 Cal. Rptr. 766].)