Obama has no clue what the bill actually says and is doing this for political reasons of building his base.
The problem is, not even those who wrote the law really cared about what the bill actually says. They passed it for the one and only reason: to build the base.
Can the states require me to do anything in the name of enforcing federal law? Can they make me dance the Macarena to prove I'm not a Russian spy or go to Jail? Since AZ has already made it an arrestable offense to not carry proof of citizenship with you at all times if you're ever at risk for being asked, maybe there's another small government policy solution out there like requiring you to carry proof of every gun which is stored in your house, even when you're not in your house, at all times, and making it an arrestable offense if you don't?
Let's be honest, the AZ law does more than enforce federal law. It criminalizes not carrying proof of citizenship on you at all times, and for people who live in Michigan or Utah, states which do not require proof of citizenship to get a driver's license, it criminalizes them any time they are accused of basically anything citizenship-related automatically, authorizing them to be arrested I believe unless they have their birth certificates on them.
Who the hell carries their birth certificates on them? Yet in Arizona, if you have a driver's license from Utah, well, that's not enough. You can be arrested.
That's not "enforcing federal law"
This is more than federal law here imo