The Arizona immigration law was blocked in three of four crucial parts by the US Supreme Court. The fourth part, allowing law enforcement officials to demand proof of legal residence, was upheld. Only eight Justices decided the case. Justice Elena Kagan, the newest and arguably the most liberal of the nine justices, recused herself, probably because she worked on the case while in the Obama administration.
The part of the law the Court upheld which allows, in fact it requires, law enforcement officials to demand proof of legal residence, does not include provisions for enforcing federal immigration law. Those portions of the law were set down on the basis that State law cannot preÃ«mpt federal law. However, the "show your papers" part isn't out of the woods yet. As one Justice pointed out, the government's case was not built on equal treatment issues. Their ruling implicitly invites further challenge on that basis. "This opinion," Justice Kennedy wrote, "does not foreclose other pre-emption and constitutional challenges to the law as interpreted and applied after it goes into effect."
The Justices seem to be saying that law enforcement can ask for anything they like, they just have to do it even-handedly. However, it's hard to see how it would be possible to ask for proof of legal residence without asking either everyone... or no one. It's equally hard to see how Arizona can expect to not see a new challenge based on violation of civil rights. The Court has virtually promised that it would accept such a challenge, and it is simply too easy to slide into profiling based on appearance.
Citizens will be challenged, and they won't have the "proper" papers on them. After all, who, besides legal aliens, carries the stuff that constitutes proof of citizenship with them? A driver's license won't do. Literally millions of illegal aliens are likely to have a driver's license that would pass muster. Few citizens carry birth certificates, passports, or naturalization papers with them. The Supreme Court will be seeing the Arizona immigration law again, and the smart money will be on the Court striking the last of it down. It's not possible to enforce what Arizona's Governor Brewer called "the heart" of this law without creating equal rights violations.