I've read the opinion, and highlighted interesting parts (and there are many). There were 4 provisions before the Court. Here's a brief synopsis of their rulings on each:
1. SB1070 made it a misdemeanor for a person to not carry his/her alien registration document (green card).
a. Held: Unconstitutional. Feds have exclusive control over immigration enforcement. States will not be allowed to supplement their own crimes on top of the fed crimes since Federal concerns drive enforcement policy.
2. SB1070 made it a crime for an "unauthorized alien" to seek work either as an employee or as an independent contractor.
a. Held: Unconstitutional. No federal sanction exists for employees seeking work, only employers knowingly hiring unauthorized people. Congress decided to focus on the employers. AZ, or any other state, cannot overrule that by making its own law in that area.
3. SB1070 gives a state law enforcement officer authority to arrest, without a warrant, someone who they believe has committed any offense that would make him/her removable.
a. Held: Unconstitutional. While noting that, generally, it is not a crime to be present in the U.S. without papers, the Court reiterated that the Feds, not the state, will determine who is removable, or who should even be placed in removal proceedings "A decision on removability requires a determination whether it is appropriate to allow a foreign national to continue living in the U.S. Decisions of this nature touch on foreign relations and must be made with one voice." AZ law enforcement has no place in this decision and therefore, the Court will not allow the provision that would allow AZ officers to arrest for perceived violations of US immigration law, to stand.
4. SB1070 requires AZ law enforcement to inquire about an arrestee's immigration status (this is the AZ papers please provision).
a. Held: Constitutional, maybe. The Court found it premature to rule on the constitutionality of this provision since it is unknown how this provision will play out in practice. State courts remain in the best position to determine whether the detention for the underlying crime is reasonable, and if not, they may conclude that the prolonged detention for the ICE check is unreasonable as well. AZ argued that the immigration check can continue after a subject is released. But, there is cautionary language for AZ here. "There is a basic uncertainty about what the law means and how it will be enforced....This opinion does not foreclose other preemption and constitutional challenges to the law as interpreted and applied after it goes into effect."
In sum. AZ lost on all four counts before the Ninth Circuit. The US Supreme Court confirmed their loss on three of the counts. As to the fourth (the papers please provision), the Supreme Court DID NOT give AZ a blank check to check papers. First, there must be a basis for the stop (i.e. probable cause or reasonable suspicion that ANOTHER crime has been committed). It will not be enough for the officer to stop based on his probable cause belief that the person is here illegally. Second, if the officers screw that up, then they can and will be sued for racial profiling and the person's defense attorney can file a motion to dismiss the criminal charges.
Can AZ law enforcement manufacture a BS charge if their real concern is the immigration status of the individual? Sure. Unfortunately, AZ v. USA seems to preliminarily allow them to do so. However, it would have been difficult for the Court to say that AZ could NEVER check immigration status (especially where the check can be done quickly). This Court said that AZ (and, obviously, other states) can do that, but if they were to do that, they need to tread carefully.
All in all, in my opinion, this is an excellent result. The pro immigration movement won outright on three of four counts and on that fourth one, they may still win, but the fight will be in the State Courts, and then, maybe right back to the US Supreme Court.