The key here is "if intended for human consumption." This is why legal highs are frequently sold as "plant food" or "bath salts." Some vendors are more careful than others, in the height of the first "wave" of designer drugs around ~2004, some vendors were as brazen as to offer "sample packs" and the like. And then Web Tryp [1] (my favorite codename ever) happened.

Many designer drugs are close analogs of schedule I substances.

[1] http://en.wikipedia.org/wiki/Operation_Web_Tryp