Never tried Heroin, but Nevada seems to have no major problems with its brothels. I think the market has decided on both: we don't want brothels in Texas, even if they are safe, and we don't want Heroin, even if making it illegal doesn't get rid of it. So, both are illegal in my state.
But neither of those seem equivalent to adding corn syrup to marinara sauce at the factory instead having mom dump in a handful of sugar to "give it the right taste". Are you going to outlaw sugar and salt the way we have successfully eradicated other dangerous drugs?