What is the difference between legalizing something and decriminalization?

After finding out Obama “inhaled quite frequently” and seeing some old videos of him talking about decriminalizing weed i started to think. Whats the difference?

My understanding is that if something is decriminalized, it means it is not a crime (and therefore you can’t go to prison if you do it or have it written in your criminal record), but it can still be illegal (and you can get fined or suffer some other penalty such as confiscation). For example, many traffic violations are not criminal, but they’re not legal either.

So decriminalization are basically any misdemeanor ?

No. In most states misdemeanors are still crimes in which you can go to jail for (usually less than 1 year per charge).

An example of something that is not a crime but still illegal is an ordinance violation.
Letting your dog shit on a public sidewalk and not cleaning it up may get you a fine but no jail time.

Many areas have adopted state misdemeanor crimes as ordinance violations. The reason for this usually is because if it is charged that way the municipality gets the fine money, not the state. So if you get a local ordinance citation for disorderly conduct, CCW, or having a small amount of weed, you are not guilty of a crime and won’t go to jail, but will get a fine and have a record. An ordinance violation, while not a crime, is still an arrestable offense.

Your mileage may vary, I am not a lawyer, this has not been legal advice.

In some European countries smoking pot and prostitution are not legal but are not crimes. This means that you will not be arrested or prosecuted or bothered in any way for doing it BUT it also means that you have no right to do it and the police can prevent you from doing it any way that is otherwise legal and there may be laws which criminalize acts which facilitate these activities.

If they find you smoking pot at their discretion they may stop you from continuing to do it as you have no legal right to do it ut they cannot arrest you for doing it. If you resist or do not cooperate then you can be arrested for resisting or not cooperating.

In other words, just because there is no penalty for doing X does not mean you are allowed to do it. It only means there is no penalty for doing it.