146.Section 99 states that universal service providers (so far as they are providing a universal postal service) are not “common carriers”. According to the common law, a “common carrier” is a person who carries all goods of all persons wishing to use his services. He is bound to accept goods that are offered to him for carriage, but he may refuse to do so if he believes that he has lawful ground for such refusal. Being a “common carrier” has implications in terms of liability. Without this exemption universal service providers might be regarded as common carriers, which could make them absolutely responsible for the safety of goods entrusted to them for carriage. This would mean that they could be liable in certain circumstances if the goods they carry are lost or damaged, even without fault on their part.
Commentary on Sections Part VI Universal Postal Service: Supplementary Section 99: Common carriers