Legally speaking, there are some things that are just too dangerous to be handled with a warning label.
If I designed and constructed a roller coaster to run off the edge of a cliff and kill all the occupants, no amount of signage saying "WARNING: CLIFF" will suffice.
Look at the amount of warinings you have to have on a ski lift or a pack of cigarettes, and these things don't kill people by design, or at least don't kill them quickly. But heroin will kill you in a minute, and it kills people every day. And this Krokodil stuff, if it is as bad as they say, winds up killing just about everybody, in a relatively short amount of time.
Sounds like evolution in action. Just faster.