For celebrities, it’s basically standard operating procedure to sign autographs for fans, but for the royal family, these rules are understandably stricter. In fact, they’re essentially banned from providing handwritten mementos, and it turns out there’s a pretty notable reason for this. Although Kate Middleton has given out hugs and allowed fans to take photographs—even selfies—with her, she’s never put pen to paper (or merch) as part of a long-standing rule that forbids the signing of autographs due to the risk of signature forgery. According to the Express, this guideline applies to all members of the British royal family, including Prince William, Prince Harry and Queen Elizabeth. The only member who’s broken protocol? Prince Charles, who’s previously scrawled “Charles 2010” on a piece of paper for a flood victim. Now, his go-to move for declining autographs reportedly involves his saying, “Sorry, they don’t allow me to do that.” Forthright yet sincere. So, should you ever find yourself in the presence of a royal, simply ask for a selfie. After all, pics or it didn’t happen, right?