No employer shall discriminate against an employee because the employee has been injured in the line of duty as a volunteer fireman, a volunteer member of the fire police or a volunteer member of an ambulance service or rescue squad, nor shall an employer discriminate against an employee injured in the line of duty as a volunteer fireman, a volunteer member of the fire police or a volunteer member of an ambulance service or rescue squad who subsequently returns to work after receiving workers' compensation benefits under the act of June 2, 1915 (P.L. 736, No. 338),¹ known as the Workers' Compensation Act.