Marie, how much difference it makes varies. Most people that want to smoke marijuana don't think it ought to be illegal, so they don't care much about the law. Also, and this is very important, when you have a law like this that only a tiny fraction of those who break ever get caught, people aren't going to worry about it much. Very few pot smokers will ever get caught. Many will do it for years, thousands of times, and never get caught. The level of deterrent effect of a law is directly proportional to the level of risk of getting caught perceived by those who contemplate breaking the law. If they think there is almost no chance of getting caught, they don't worry so much about getting caught, especially when all they will get in the unlikely event that they do get caught is a basically a slap on the wrist.
Our laws against marijuana possession have very little deterrent effect. Our laws against other drugs don't have much deterrent effect either, but I think they have a little more than marijuana laws. If someone gets caught with a drug like cocaine or meth or heroin, it's generally going to be a felony and the punishments are more severe than those for possession of marijuana. Not only that but the police are looking more for these drugs and people involved with them are a lot more likely to be trouble and the types who bring unwanted attention from the police than those who only mess with marijuana. This increases the perceived risk of getting caught. Now, someone who isn't deterred by the very real possibility of becoming a lifelong hard drug addict probably isn't going to worry much about the fairly slight risk of getting caught, but still I think these laws banning possession of those drugs deter more than the laws banning marijuana possession. None of these laws are going to deter people anywhere close to as much as laws against crimes people have a good chance of getting caught committing, like your shoplifting example. You might get away with shoplifting once or a few times, but sooner or later you are going to get caught. If you smoke marijuana every day odds are you will never get caught if you are just a little bit careful about it.
“If you smoke marijuana every day odds are you will never get caught if you are just a little bit careful about it.”
I don’t know, you have to buy it. Hiding out in your house you may be pretty much fine, although there is still some risk. But you have to buy the stuff.