IIRC, several decades ago, fed.gov put an additional tax surcharge on airline tickets, and included a provision explicitly prohibiting the airlines from disclosing this new tax. The airlines refused to participate in this secrecy, and basically said "If you every TRY to prosecute, we WILL demand a jury trial and we WILL include your actions in our advertising."
I don't remember anyone being prosecuted for spilling the beans . . .