The famous code has been broken, and the Las Vegas Convention and Visitors Authority is out for revenge, Sin City style.
"What happens in Vegas, stays in Vegas" was breached this week when photos of Britain's Prince Harry, cavorting naked in a Las Vegas hotel suite, were published on celebrity news website TMZ, causing an international uproar.
"FOR SHAME!" shouts a full-page ad in Friday's USA Today placed by the agency. "To those who traded in their pledge to their Las Vegas brethren, we deplore you!"
The ad continues: "We are calling on you, the defenders of what happens in Vegas staying in its rightful place -- in Vegas. We are asking for a shun on these exploiters of Prince Harry. We shall boycott partying of any kind with them. No bottle service. No bikini clad girls. No Bucatini from Batali. In other words, we will not play with them anymore."
Dozens of people had tweeted to #knowthecode by early afternoon on Friday in response to the ad.
"Las Vegas is a place to celebrate adult freedom, freedom that even celebrities and royals can enjoy," Cathy Tull, senior vice president of marketing for the convention and visitors authority, said in a statement. "For everyone's sake, it's important that 'What Happens in Vegas, Stays in Vegas.'
"However, in moments of enthusiasm, actually keeping memories in Las Vegas takes commitment," Tull said. "Today's ad was a cheeky reminder to all our visitors that it's important to 'know the code', and most importantly, 'protect the code'." (Reporting by Dan Burns; Editing by Daniel Trotta and Xavier Briand)