29 U.S.C. § 1842

No person shall utilize the services of any farm labor contractor to supply any migrant or seasonal agricultural worker unless the person first takes reasonable steps to determine that the farm labor contractor possesses a certificate of registration which is valid and which authorizes the activity for which the contractor is utilized. In making that determination, the person may rely upon either possession of a certificate of registration, or confirmation of such registration by the Department of Labor. The Secretary shall maintain a central public registry of all persons issued a certificate of registration.