19 U.S.C. § 507

(a) Every customs officer shall— (1) upon being questioned at the time of executing any of the powers conferred upon him, make known his character as an officer of the Federal Government; and (2) have the authority to demand the assistance of any person in making any arrest, search, or seizure authorized by any law enforced or administered by customs officers, if such assistance may be necessary. If a person, without reasonable excuse, neglects or refuses to assist a customs officer upon proper demand under paragraph (2), such person is guilty of a misdemeanor and subject to a fine of not more than $1,000. (b) Any person other than an officer or employee of the United States who renders assistance in good faith upon the request of a customs officer shall not be held liable for any civil damages as a result of the rendering of such assistance if the assisting person acts as an ordinary, reasonably prudent person would have acted under the same or similar circumstances.