In Arizona v US concerning Arizona's SB1070 has spurned a lot of speculation. Both sides of the law have claimed a form of victory in the decision and opinions handed down by the Supreme Court.
The decision, majority, and dissenting opinions aggregate to seventy-six pages. All of them are partially dissenting, partially assenting.
Four provisions of the State Law came into contention. Three of the provisions were struck down on the sole concept of preemption. Federal Laws already on the books preempt state laws in regards to immigration. The US Constitution provides a clear clause in Article 1 Section 8 that states the Congress has the sole authority in determining naturalization and immigration laws.
This decision enforces the US Constitution's supremacy over state laws in accordance to Article 6 Clause 2 when used in application to the explicitly stated enumerated powers. Those who support the US Constitution as the supreme law of the land should support this decision, even though they approve of the state level law.
The court decision does little for or against the border states. The federal laws are on the books and should be enforced. States are allowed to enforce federal laws, but not allowed to change them. That makes sense. The question left hanging is can states sue the federal government for not enforcing their own laws.
The provisions struck down include the stipulation that Arizona made being in the country/state illegally a state-level crime. The violation already serves as a federal crime, no state level crime is necessary. The provision was merely to raise attention to the fact the federal courts and enforcement officials were refusing to do their jobs. Striking down this provision, in effect, does nothing.
Making it a crime to hold a job while in the country illegally is already against a federal law. State and federal laws targeting employers already exist as well. Striking down this provision also does nothing.
The one provision struck down that actually serves as a blow to the border states is the decision that state and local level law enforcement officials must grant 4th and 5th Amendment rights to non-citizens who are in the US illegally. No searches, seizures, or arrests without warrant are allowed to border states since they allegedly preempt federal laws.
However, the most contentious of the four provisions remained upheld. If somebody is stopped under suspicion of breaking another law, include during a routine traffic stop, local law enforcement officers can inquire citizenship and/or legal residency status. Any person detained must have such status verified before being released. If found in the country illegally, they can be referred to the US Federal authorities for prosecution. If the federal officials defer to prosecute, the state officials can prosecute and jail those personnel as appropriate, making the judgement fit the crime.
To an extent, the decision sends a message to border states. It tells them "you cannot defend yourselves". However, it also sends the message "you can enforce the federal laws, as long as you do so in accordance with those federal laws and include the proper federal authorities".
The best response border states can employ at this point is to ease up on Castle Doctrine laws. If somebody in a border state believes their property is being invaded, they should be allowed to defend their property, shooting on sight. Of course, I also advocate ranchers on the borders being allowed to own and employ M2 .50Cal machine guns to protect their sovereign property.
Mental Aikido: USSC Decision -- Impact on Border States