I think that's a bit pedantic. In context, it is quite obvious the comment is referring to the fact that heroin is illegal recreationally, and thus, not widely available.

Also, while I realise this discussion spans other countries, heroin is not prescribed in the US. In Canada, it is largely prescribed to heroin addicts and not as a pain management mechanism. While I believe it is prescribed in England and probably Europe, the point stands that heroin is illegal for most people in most places.