The Judiciary is the one branch that totally confuses me.
Sometimes a single low-level federal judge can strike down a law instantly and nationally on the grounds if violated another law. In this case, a higher-circuit panel of three judges strike down a law that violated the Constitution - but the law stays in place for a while until some other judges weigh in, and even if it sticks it only applies to a portion of the country?
The only time a Federal judge can "strike down" a law "instantly" is via something called a preliminary injunction, which only comes into play when it's grossly obvious the law is likely to be ruled unconstitutional AND there's ongoing harm demonstrated from the law being enforced. This requires a higher standard of proof. Otherwise, the court has to hear both sides and rule on the merits like any other lawsuit before taking any action, which they still have to do after the injunction anyway.
In this case, the law stays in place because the exact same judge that ruled it unconstitutional also ruled that letting that ruling take place immediately would cause too much churn for CA law enforcement. He made his ruling, the AG asked for a stay until he could appeal, the stay was granted, and now the AG is appealing. The AG lost, but also has the option of asking for an en banc rehearing of the case or an appeal to SCOTUS.
If appeals run out and the AG was still on the losing side, the stay would no longer be a thing.
Also, things only apply to part of the country because the only court with jurisdiction over the whole country is SCOTUS. Every court (usually) has to follow its own prior rulings or precedent. It also has to follow the prior rulings of all higher courts. Everyone has to follow SCOTUS precedent. Higher courts are supposed to take cases in order to resolve blatant splits in the rulings of their inferior courts, but this doesn't happen overnight. Also, courts can only take cases presented to them, so even if there is a split, someone has to sue and appeal up to the higher court for them to resolve the split.