 The "Four-inch regulation" or "Four-inch law" is a colloquial name for a regulation issued by the U.S. FDA in 1975, restricting the sale of turtles with a carapace length less than four inches (10 cm).The regulation was introduced, according to the FDA, "because of the public health impact of turtle-associated salmonellosis".Cases had been reported of young children placing small turtles in their mouths, which led to the size-based restriction.