There are parts to the law which won’t hold up. If you stop for a hitchhiker....you have to ask about nationality...otherwise, you could be accused of transporting an illegal. This particular part of the law has looked upon as a bit stupid by the locals.
The rest of the law will be challenged...but I suspect most will stand up in court as well as the Arizona law.
Isn't hitch hiking itself one of those unenforced illegalities?