People can inject just about anything they want into themselves (the Controlled Substances Act being the exception). The issue is when 'doctors' get involved and use their position of trust to scam, harm, and kill. These regulations control what doctors and companies can do, not what individuals can do.
btw: "mainlining bleach" is not an exaggeration: http://www.youtube.com/watch?v=H7tkyK8r3yw