The late comedian George Carlin drew up a list of seven words you can never say on broadcast television. No one has ever tried to enumerate the combinations of letters and numbers that can’t be printed on a government-issued vanity license plate.

Policing that seven-letter medium falls to a group of state motor vehicle employees who have a knack for solving word puzzles, a Mencken-like command of modern slang, and the disposition of a barroom bouncer.

Phonetically arranged characters that sound like four-letter words are the easiest to weed out. Vanity reviewers know to flag certain colors, area codes and other numbers associated with street gangs and Adolf Hitler.

Other submissions require a trained eye—or the help of online slang references—to unscramble.

Take, for example, the term U EJIT. A DMV reviewer in California recently rejected it saying it sounds too much like the word that an Irish driver might blurt out to a motorist who cut him off (“You eejit,” meaning, “you idiot”).