49 U.S.C. § 14913
Conclusiveness of rates in certain prosecutions
When a carrier publishes or files a particular rate under section 13702 or participates in such a rate, the published or filed rate is conclusive proof against that carrier, its officers, and agents that it is the legal rate for that transportation or service in a proceeding begun under section 14902 or 14903. A departure, or offer to depart, from that published or filed rate is a violation of those sections.