actually they should legalize it all. pots easy not nearly as bad as either cigaretts or alcohol.
the other, while presenting major health risks (among other problems), are a self solving problem. if they were legal they would be cheap and plentiful, if they were cheap and plentiful, then the users could get much more with much less effort. so they OD much sooner.
I can't remember the exact % but something in the area of 90% of those charged of a drug crime are likely to re-offend. with enforcement, trial, treatment, incarceration, supervised probation,.... all costing 10's of thousands per offender.
however with the OD it costs about $300 bucks for the crematorium. and guess what, 0% repeat offenders.
we could tax the hell out of it and it would still be about a 10th the price it is now.
this would help in a few ways.
first you could use some of this tax money to ensure counseling and treatment are available for those who decide for themselves they really want to quit (really the only ones who it will work on, those who are forced into treatment rarely stay drug free).
second is just basic economics. right now your average crank junkie has to steal 3 or 4 car stereos a day just to keep his habit up. however, since a few dollars worth of chemicals can make what sells now for several thousand dollars. he could get a weeks worth for just one or 2 stereos, this is a huge drop in the crime rates, and doesn't even include the drop directly from legalization{if you have less things that are a crime you naturaly have less crime being comited}, also since he's not likely to save it for a weeks worth but more likely will do it all right away, he is much more likely to OD sooner (see above figures on repeat offender)
the other thing is these people who do drugs, (since they wouldn't have to hide it anymore) would be publicly more visable, they would be excellent examples to kids. without our safety net restricting supply, of those who do drugs, the % who die from it will go up. nobody else can be seen to blame but the drugs or the user, a very clean clear msg. much better than the gov't efforts to get kids to choose to say no. things like the movie reefer madness, or the dare program. the d.a.r.e. program may work on dumber kids but smarter kids are able to figure out that most of the examples of lives that are ruined by drugs are more acurately ruined buy drug law.
of course there are also the recreational users who keep their usage under control, don't do it at work, and basicly handle drug use just like a social drinker handles alcohol (as aposed to the type of user discribed above who handle drugs like an alcoholic handles alcohol). so far the only real reason given for getting involved is that it's illegal (not really a relivant argument in a "should it be legal" argument), or that it enables the adicts to use (kind of a lame argument when you figure that the only real effect I can see them having is tipping the ballance of suply and demand making the drugs more expensive for the addict)