The district courts, together with the United States District Court for the District of the Canal Zone, the District Court of the Virgin Islands, and the District Court of Guam shall have jurisdiction, for cause shown, to restrain violations of section 215 of this title, including in the case of violations of section 215(a)(2) of this title the restraint of any withholding of payment of minimum wages or overtime compensation found by the court to be due to employees under this chapter (except sums which employees are barred from recovering, at the time of the commencement of the action to restrain the violations, by virtue of the provisions of section 255 of this title).