I will have to admit that am always abit surprised to see objections being raised to my comments that have nothing to do with what I said. I mentioned or suggested nothing about laws being just or unjust. My only suggestion was that social science can be used to look at various aspects of our society and come up with conclusions to reduce crime. That suggestion would apply whether the laws are just or not.
Whether a law is just or unjust is also a conclusion that can be reached by social science. There are studies right now, for example, that take a look at how the death penalty is applied and changes are being made to make it more equitable.
The OP didn't ask anything about whether a given set of laws, such as drug laws, are inherently unjust, so I'm not going to address that issue. Again, this matter is already being looked at by social scientists and others, who are concluding, for example, that the evils caused by alcohol consumption are much greater than those caused by the illegal drug marijuana, and there are movements in various states to allow legal use.
I was a parole/probation officer for 7 years in MD and most of the parolees I had were not in prison for drugs, mostly crimes of violence and felony theft, some of it related to drug use which they used in an attempt to explain their behavior.
This website, part of the National Criminal Justice Reference Service, shows that most offenders in state prisons are there for crimes of violence, followed by property crimes, with drug offenses coming in third. Most prisons in the country, of course, are run by the states.
http://www.ojp.usdoj.gov/bjs/prisons.htm