Article 16
Prohibitions
1. Commercial papers, samples, and printed papers which do not fulfil the conditions laid down for articles of these categories in Article 5 of the present Convention and in the Regulations contemplated in Article 20 are not to be forwarded.
2. If occasion arise, these articles are sent back to the Post Office of origin and returned, if possible, to the sender, save where, in the case of articles prepaid at least partially, the Administration of the country of destination is authorised by its laws or by its internal regulations to deliver them.
3. It is forbidden:
(a) Samples and other articles which, from their nature, may expose the postal officials to danger or soil or damage the correspondence.
(b) Explosive, inflammable, or dangerous substances; animals and insects, living or dead, except in the cases provided for in the Regulations contemplated in Article 20 of the Convention;
(a) Coin;
(b) Articles liable to Customs duty;
(c) Articles of gold and silver, precious stones, jewelry and other precious articles, but only where their insertion or transmission is forbidden by the legislation of the countries concerned;
(d) Any articles whatsoever of which the importation or circulation is prohibited in the country of destination.
4. Packets falling under the prohibitions of the foregoing paragraph 3, which have been erroneously admitted to transmission, should be returned to the Post Office of origin, except in cases where the Administration of the country of destination is authorised by its laws or by its internal regulations to dispose of them otherwise.
Explosive, inflammable, or dangerous substances, however, are not returned to the country of origin; they are destroyed on the spot under the direction of the Administration which has detected their presence.
5. The right is, moreover, reserved to the Government of every country of the Union to refuse to convey over its territory, or to deliver, articles passing at reduced rates in regard to which the laws, ordinances, or decrees which regulate the conditions of their publication or circulation in that country have not been complied with, or correspondence of any kind bearing ostensibly inscriptions, designs, etc., forbidden by the legal enactments or regulations in force in the same country.
