How do you know that? We can't eliminate opiate deaths completely but we can make them as safe as possible. Restricting access isn't working.
I am not against drug legalisation, on libertarian grounds. If you want to kill yourself, kill yourself, it's your life not mine. But I don't buy that banning drugs results in more harm that making them freely available.
And it's very paradoxical for liberal societies to want to ban or heavily control the use of alcohol and cigarettes and to consider legalising hard drugs at the same time.