Section 15. Violation of Duty to Bargain Collectively. — It shall be unlawful for any employer to refuse to bargain collectively with the representative of his employees, or to declare a lockout without having first bargained collectively with the representative of his employees, in accordance with the provisions of this Act. Any employee whose work has stopped as a consequence of such lockout shall be entitled to back-pay.

The refusal of a labor organization to bargain collectively with an employer or the declaration of a strike by such organization without having first bargained collectively with an employer pursuant to this Act, shall be sufficient cause for the Court of Industrial Relations to deny to said union all rights and privileges under this Act. Any employee who participates in such strike shall lose his status as an employee for the purposes of this Act.

The declaration of a strike by a labor organization or a lockout by an employer where no previous notice of a desire to negotiate an agreement has been served upon the other party as provided in Section 14, shall be deemed prima facie evidence of a violation of the duty to bargain collectively.