It's not the legalization of marijuana, rather, the decriminalizatoin of it. It would still be illegal, like parking in the red zone or driving without a license (or a 17 year old drinking a beer here). If you get caught with less than 7 grams, you get it taken away from you and a fine.

It's a shame the US would be upset when they consume the most illicit drugs in the WORLD (overall volume and per capita).