It is a stupid law but I feel people are overthinking this.

For compliance the os has to provide an age category to an application and an interface for the user to enter this data. We already have an api to provide information to applications. it's called the filesystem. and an interface to enter the data, that's called the shell. so everything is already there. If the user lives in california and wants to be compliant (wait a minute, let me stop laughing) all they have to do is put a file somewhere with a age category in it. if the application can't find it. well it's not their fault the law is stupid.