Naturist pictures are not considered pornography. This conclusion was reached by the United States Supreme Court in a 1958 decision involving the United States Postal Service and questions regarding the legality of delivering naturist magazines.
The Supreme Court ruled that photography categorized as "nudist" is not pornographic unless the images are explicitly sexual in nature. The Court used as its standard the Comstock Laws, which define the parameters applicable to pornographic content. Specifically, obscenity is material whose dominant theme taken as a whole appeals to the prurient interest. The Court decided that naturist imagery falls outside of this definition; it is therefore court-protected and not considered obscene.