When certification of a representative of employees for collective bargaining purposes has been made by proper federal or state authority, it is unlawful during the effective period of such certification for any employee, representative of employees, or labor organization to conduct a strike or boycott against the employer of such employees or to picket any place of business of the employer in order, by such strike, boycott, or picketing to:
Minn. Stat. § 179.27
1945 c 414 s 2