Snakes don't get much legal protection because of public prejudice, such as hate, fear, wrong assumptions (such as "they're dangerous" or "they are pests"), and ignorance of the fact that many snakes are of good use (they keep rodents in control and are an important link in the ecosystem). Occasionally they get protection, but usually only after they become really rare; also sometimes they get accidental protection (e.g., in national parks, forests, preserves, and game parks).
There are usually regulations governing the keeping of dangerous snakes. These can be national or local laws and are designed to protect the public from danger. Species involved include the vipers and cobras, certain back-fangs, and some large boas and pythons. Some nit-witted officials enforce a total ban on all snakes within their area of juridisction for no good reason. Kind of idiotic, isn't it?
Disturbed Natural Habitats
Starting in the 1950s, western countries developed, cities grew, suburbs enchroached on agricultural land, and highways cut into forests. Agriculture was modernized with pesticides and by the draining of marshes. A balance of nature made over millions of years was broken. Affected were the populations of snakes (especially in forests and woodlands). As we continue to destroy natural land, all animal populations (including snakes) will dwindle.
Some Legal Restrictions
Various authorities restrict the keeping of snakes for public display, for sale or for other commercial activities, or the release of exotic species into the wild. These restrictions are not likely to affect amateur and beggining snake owners. Apart from the above legal requirements, snake-keepers are under a moral obligation not to make their hobby objectionable to the public at large. Just remember that some people aren't very fond of snakes, and their opinions should be respected.