Contents Index
C000 General Information
C020 Restricted or Nonmailable Articles and Substances

C021 Articles and Substances Generally


C021 describes the legal regulations prohibiting or restricting the mailing of certain items such as liquors, abortive and contraceptive devices, odd-shaped items in envelopes, motor vehicle master keys, and locksmithing devices.

1.0 Restricted MatterGeneral

Restricted matter is an article or substance prohibited or limited by Title 18, U.S. Code (liquors, abortive and contraceptive devices, odd-shaped items in envelopes, motor vehicle master keys, and locksmithing devices). It also includes matter not otherwise described in C020 that is restricted by 18 USC 1716(a) because it may, under conditions encountered in the mail, be injurious to life, health, or property (obnoxious odors, liquids, powders, and battery-powered devices).

2.0 Nonmailable Articles and SubstancesGeneral

2.1Basic Information

The basic premise of the postal mailability statutes is that anything “which may kill or injure another, or injure the mails or other property...” is nonmailable. Several statutory exceptions to this rule permit mailings of otherwise nonmailable matter under specified conditions. Statutory exceptions apply to live scorpions, poisonous drugs and medicines, poisons for scientific use, switchblade knives, firearms, motor vehicle master keys, locksmithing devices, and abortive and contraceptive devices. The statutes also provide that the USPS may, by regulation, permit the mailing, under required conditions of preparation and packing, of potentially harmful matter not “outwardly or of [its] own force dangerous or injurious to life, health, or property.” The standards in C021 summarize the statutory prohibitions and exceptions. The mailability standards that apply to perishable, hazardous, and restricted matter are detailed in C022, C023, and C024, respectively. Publication 52, Hazardous, Restricted, and Perishable Mail, contains additional clarification and further describes the conditions of preparation and packaging under which the USPS accepts for mailing potentially harmful matter that is otherwise nonmailable. Publication 52 also contains detailed information on the mailability of specific hazardous materials.

2.2Mailer Responsibility

The mailer must comply with applicable postal laws and regulations governing mailability and preparation for mailing, as well as nonpostal laws and regulations on the shipment of particular matter.

2.3USPS Refusal

USPS employees may refuse an article for mailing if the content of the article is described by the mailer or otherwise revealed to be nonmailable.

2.4Other Laws and Regulations

Particular matter may be mailable under postal statutes and regulations, but customers may have responsibilities under nonpostal statutes and regulations concerned with possession, treatment, transmission, or transfer of such matter (e.g., 49 CFR 100-185 (Department of Transportation Regulations); the Comprehensive Drug Abuse Prevention and Control Act of 1970 (Public Law 91-513), 21 USC 801, et seq.; and the Gun Control Act of 1968 (Public Law 90-618), 18 USC 921, et seq.).

2.5Statutory System

18 USC 2510, et seq., constitutes a statutory system of regulating interception of wire, oral, or electronic communications. Any person contemplating the mailing of a device primarily useful for surreptitiously effecting such interception should consider the provisions of 18 USC 2510, et seq., particularly section 2512. This statute makes it a crime, except as otherwise provided in 18 USC 2510, et seq., for a person intentionally to send through the mail any device whose design that person knows, or has reason to know, renders the device primarily useful for surreptitious interception of wire, oral, or electronic communications. The statute does not declare that such a device in itself constitutes nonmailable matter but, as indicated, provides criminal penalties for the act of intentionally mailing it.

2.6Authorizing Mailability

A postmaster may decide whether articles and substances other than written, printed, or graphic matter are nonmailable and, where appropriate, is authorized to refuse to accept for mailing such matter determined to be nonmailable. The mailer may seek a review of the postmaster’s decision by the PCSC. The mailer may file a written appeal of the PCSC ruling with the USPS Recorder, Judicial Officer, with a copy or description of the determination or ruling. The rules of procedure for the determination of such appeals are in 39 CFR 953.

2.7Protecting Employees

A postmaster may take any step reasonable and necessary to protect USPS employees and equipment from potentially dangerous or injurious materials or substances found in the mail.

2.8Applicability to Military Postal System

C020 applies to the military postal system, its personnel, and undelivered mail that is or has been in the official custody of that system and its personnel. References to the Inspection Service refer to the Postal Inspection Service and its authorized employees, not to military investigative services.

3.0 Injurious and Harmful Articles


Except as provided in this document, any article, composition, or material is nonmailable if it can kill or injure another or injure the mail or other property. Harmful matter includes, but is not limited to:

a. All types and classes of poisons, including controlled substances.

b. All poisonous animals except scorpions mailed for medical research purposes or for the manufacture of antivenom; all poisonous insects; all poisonous reptiles; and all types of snakes, turtles, and spiders.

c. All disease germs or scabs.

d. All explosives, flammable material, infernal machines, and mechanical, chemical, or other devices or compositions that may ignite or explode.

3.2Hazardous Materials

Harmful matter also includes regulated hazardous materials as defined in C023 that are likely to harm USPS employees or to destroy, deface, or otherwise damage mail or postal equipment.This includes materials such as caustic poisons (acids and alkalies), oxidizers, or highly flammable liquids, gases, or solids; or materials that are likely, under conditions incident to transportation, to cause fires through friction, absorption of moisture, or spontaneous chemical changes or from retained heat from manufacturing or processing, including explosives or containers previously used for shipping high explosives with a liquid ingredient (such as dynamite), ammunition, fireworks, radioactive materials, matches, or articles emitting obnoxious odors.

4.0 Marking


Except for firearms and switchblade knives, controlled substances, radioactive materials, and motor vehicle master keys and locksmithing devices, the identity of the content of anything mailed under C020 must be plainly and durably marked on the address side of each mailpiece as a condition of mailing. When the content is a hazardous material as defined in 49 CFR, each mailpiece must be marked as required in C023.


For any matter mailed under the provisions in C020, the recipient’s name and address must be affixed or applied directly to the mailpiece using a material or method that is not water-soluble and not easily smeared or rubbed off. Except for diagnostic specimen mailpieces using a business reply mail format and nonregulated materials, a return address that includes the sender’s name and address must appear on all matter mailed under C020. The return address, when required, must be applied using a material or method that is not water-soluble and not easily smeared or rubbed off.

4.3Warning Label

Except for controlled substances mailed under C024, any label or other marking required by federal law or the regulation of any federal agency must be securely affixed or applied to the address side of each mailpiece. See C023 for the warning label requirements that apply to the mailing of hazardous materials.

DMM Issue 58 Updated 12-9-04