The snails are illegal in the U.S. because they reproduce quickly, eat native plants (as many as 500 different varieties), and can transmit meningitis via their mucous trails.
“In 1966, a Miami boy smuggled three Giant African Land Snails into the country. His grandmother eventually released them into a garden, and in seven years there were more than 18,000 of them. The eradication program took 10 years, according to the USDA.”
Yikes! This is a good example of an “invasive species.” The article also notes that “people who have the snails without knowing they are illegal will not face punishment.”