The federal government strictly regulates immigration, when the animals entering the country are humans. Australian saltwater crocodiles are a different story. This article describes the debate over a bill to regulate the importation of nonnative animals:

Bordallo’s bill would establish a method to assess all nonnative animals in the United States, excluding the common ones like dogs, cats, goats and horses.

Each would be approved or blacklisted, based on the danger it poses the economy, environment or other animals.

Although matters such as regulating chickens are best left to states and local governments, bringing dangerous wildlife into the country ought to be restricted at the national level. This effort should focus on prohibiting those animals that are a danger, not on determining the environmental impact of every hedgehog. I’ll be happy if the federal government keeps out crocodiles and lets states do the rest.