Postal laws and regulations define the procedures that postal authorities and is also called postal law. All Universal Postal Union (UPU) member countries adopt The Postal Act of UPU, although specifics can vary country by country. Non UPU members have their own Postal law. Generally, in the international postal relations, UPU act is maintained, but in domestic service, every Postal Authority follows local laws.
References
Postal laws and regulations Wikipedia(Text) CC BY-SA