43 Pa. Stat. § 206m
No court of this Commonwealth shall have jurisdiction or power in any case involving or growing out of a labor dispute to issue a temporary restraining order or temporary injunction where employes are defendants, or the employer, either in anticipation of, or at or subsequent to the inception of, a labor dispute, has employed persons or assigned other employes to perform the duties of employes then or subsequently not working because of the labor dispute, unless, prior to the granting of such restraining order or temporary injunction, the said employer has discharged such persons and reassigned the other employes back to their former duties, and such facts shall be averred under oath in the application for the temporary restraining order or temporary injunction, and no temporary restraining order or temporary injunction shall issue unless it contains the following provision:
"This order (or injunction) shall remain in effect only so long as .......... (name of employer) shall not employ persons, or transfer employes to perform the duties of those now or hereafter not working because of the labor dispute."
43 P.S. § 206m