Legal Question in Consumer Law in California

You are thinking of only one, and the most commonly used, meaning of "tariffs." That is taxes levied by governments on imports and exports of goods. That is now, however, the only meaning and it is not the meaning the freight companies are using when they tell you that certain categories of freight incur additional charges due to tariffs. The tariffs they are referring to are the formal terms, conditions and schedule of charges maintained by the shipper and regulated by the Interstate Commerce Commission and Dept. of Transportation. In particular the DOT imposes significant regulations on transport of many materials, and shippers impose additional fees for transporting those things. The list of fees and when they are charged are contained in the shipper's tariffs. You can find the UPS Tariffs/Terms and Conditions of Service here for example: https://www.ups.com/media/en/terms_service_us.pdf