Mail articles containing literature or advertisements concerning devices to produce unlawful abortions, are prohibited from the mails by 18 U.S.C. 1461 , and shall be retained by, or delivered to, the Postal Service for disposition under the postal laws and regulations. If the Postal Service determines in any case that it is proper to release the material to the addressee, it shall be submitted for Customs treatment before delivery.
19 C.F.R. §145.52