How does one find regulations that are specified by the United States Code? For example, 22 USC § 288b says:
§288b. Baggage and effects of officers and employees exempted from customs duties and internal revenue taxes
Pursuant to regulations prescribed by the Commissioner of U.S. Customs and Border Protection with the approval of the Secretary of the Treasury, the baggage and effects of alien officers and employees of international organizations, or of aliens designated by foreign governments to serve as their representatives in or to such organizations, or of the families, suites, and servants of such officers, employees, or representatives shall be admitted (when imported in connection with the arrival of the owner) free of customs duties and free of internal-revenue taxes imposed upon or by reason of importation.
I am unable to locate any relevant "regulations prescribed by the Commissioner of U.S. Customs and Border Protection with the approval of the Secretary of the Treasury" in the Code of Federal Regulations; do they exist, and, if so, where?
A general answer to the question is obviously preferable, but if someone is able to find the specific regulations in the example without being able to answer the general question, that is also helpful.