When it comes to the animal that is illegal to keep as a pet, there's several animals that are illegal for people to keep as pets.
The following animals are illegal for humans to keep as pets.
Native wildlife animals, like deer, raccoons, squirrels, and birds of prey are widely illegal for humans to keep as pets.
Small turtles, as under FDA law, any turtle that has a shell that is smaller than 4 inches is illegal to keep or sell as a pet nationwide because they have the potential to spread salmonella.
Venomous and dangerous reptiles like alligators, crocodiles and venomous snakes like vipers and cobras are illegal to keep as pets in almost all jurisdictions without any specific commercial or educational licenses.
And primates like apes, chimpanzees and monkeys are also illegal in most states to keep as pets or at least heavily restricted as being kept as pets in some places.
And large carnivores that are illegal to keep as pets include lions, tigers, bears and other undomesticated big cats are often banned nationwide, most specifically under the federal Big Cat Public Safety Act.
The regulations on these animals being kept as pets also varies widely and is highly localized.
An animal that is illegal to be kept as a pet in one state or city, may be perfectly legal with a permit in another state or city.
And some other countries other than the United States may have no laws on a specific animal being kept as a pet when the United States makes it illegal.
So you have to check your local laws about any restrictions on certain animals being kept as pets and any permits that you may or may not need.