Marijuana should be made legal because it is less harmful than alcohol. Regulation should be similar to how tobacco and alcohol regulation works: high tax, detailed records, and ID checks.
Harder drugs such as like cocaine, heroin, and meth because of the extremely high health risks. These risks include the staggering addiction rates and likelihood of overdose. Additionally, many of the unfortunate souls who abuse these hard drugs make themselves burdens on society. Oftentimes, use of the drugs becomes expensive, destabilizes the users who are more likely to be fired from their jobs, and forces them to turn to government entitlements or to mooch off of family and friends.
However, the users of hard drugs should not be seen as criminals of a similar caliber of burglars or embezzlers. Those who become addicted to drugs are victims and sending them to jail for years would only serve to exacerbate the issue by forcing them to turn to crime, because who wants to hire a convict? Instead, treatment options should be open to the users, similar to how people convicted of assault may have to attend anger-management classes.