no way!!!!!
if you really want to make it MORE difficult for drug users to be able to get drugs, you legalize it and control the distribution.  It's harder for kids to get Alcohol than it is for them to pick up a bag of drugs---any drugs... why??? because the black market doesn't give a fuck. If you decriminalize drugs put regulations on them and remove the negative propaganda, you can create a safer environment for drug distribution, drug education, and drug use.
comparison:
Black market:
-age restrictions -- none (sole discretion of the drug dealer --- and if steppenwolf is right, the pusher man don't care)
- quality assurance -- none -- you go to buy some E, but end up with crystal meth, or a cut of this a cut of that
-safety -- none-- with drugs being illegal you'll have on the dealer's side cartels wagering war on the protectors of the law, war means violence, war means not safe. You've also got users who will be running from the law, high speed pursuits, violence, etc etc...
-information -- unreliable at best -- you go to your dealer to pick up something nice for the weekend, the dealer tells you you've gotta take 'x' amount, do a little this do a little that, whatever, probably from personal experience (at least the person is alive to tell you what they did).  But it's doubtful that drug dealers will be completely honest with the buyer... example on how drug dealers are full of bullshit -- every  time they get 'new' drugs they are 3 or 5 times better than the last time they had the drugs... if that were the case the next bag of chronic you buy should be so potent that you get high just from smelling it. (do you understand what i'm saying)
can you think of any other concerns to compare?  post em up.
now vs. a decriminalized system
age restrictions-- yes and effective (at least insofar as the quality of id checking) don't think someone under the age of 25 should be able to take acid, easy, only 25 year olds can buy it.  You can put strict punishments up for sale to minors, or buying drugs for a minor. I'm going to get $30,000 fine for buying  a kid an 1/8 of pot, even if i think the kid should be able to smoke it, it's not really worth it for me to 'stick it to the man' and buy the kid some pot.
-quality assurance -- you won't have to be afraid of getting bunk shit if drugs were sold over the counter, when was the last time you were afraid that the bottle of captain was going to be anything other than 70 proof rum? With this you'll also get measured 'doses'.
safety-- the danger applies to the drug salesmen, we've already seen california put in pot vending machines, and we've seen people hold up the vending machine... but overall, i've got to say it'll be safer than what we have today...
information -- if drugs are decriminalized, you can get rid of the negative propaganda surrounding drug use. you can have actual science provide legitimate information about the dangers risks and effects.  you'll have the measured doses -- while they may not be accurate for EVERYONE, we've still managed to figure out what constitutes a 'normal' dose for pretty much everything -- prescriptions to cereal.  If you're afraid of something, the BEST thing you can do is learn more about it. Once you've learned about something then you can rationalize your fear.   remember the girl on the Maury show who was afraid of pickles? Simply because you're afraid of something doesn't make it dangerous.  Now if they did research on pickles and found that if you have too much dill on your pickle and it opens up a demon portal to the underworld and beasts would run out and destroy the world, maybe you could justify the fear.    basically what i'm saying is fear with out knowledge is just emotion, and shouldn't be used as evidence as truth of something.