49 CFR §172.303

1. (a)No person may offer for transportation or transport a package which is marked with the proper shipping name, the identification number of a hazardous material or any other markings indicating that the material is hazardous (e.g., RQ, INHALATION HAZARD) unless the package contains the identified hazardous material or its residue.
2. (b)This section does not apply to—
   1. (1)Transportation of a package in a transport vehicle or freight container if the package is not visible during transportation and is loaded by the shipper and unloaded by the shipper or consignee.
   2. (2)Markings on a package which are securely covered in transportation.
   3. (3)The marking of a shipping name on a package when the name describes a material not regulated under this subchapter.
   4. (4)Identification number markings on a cargo tank motor vehicle containing a petroleum distillate fuel in accordance with § 172.336(c).