“Short term this decision keeps immigration as a front-and-center issue in the 2012 election, because it didn’t provide closure and essentially told both sides to go at it,” says Peter Brown, assistant director of the Quinnipiac University Polling Institute. “In the long term, what it means is that state legislatures, at least in some states, will likely have to deal with this in terms of whether they get an Arizona-style law that includes the parts that got the seal of approval.”
The Supreme Court did draw some definitive lines for states pondering Arizona-style laws. Making it a state crime for an illegal immigrant to seek work and walk around without immigration papers, for example, is not allowed. Also not allowed is giving police authority to arrest people for immigration-related crimes.
"Federal law makes a single sovereign responsible for maintaining a comprehensive and unified system to keep track of aliens within the nation's borders,” Justice Anthony Kennedy wrote in the 5-to-3 majority opinion. Justice Kennedy noted specifically that if the court allowed Arizona to arrest people for not carrying papers attesting to their legal residency status, "every state could give itself independent authority to prosecute federal registration violations."
On the “papers, please” aspect, the court in effect said it needs to be tested after implementation, since the justices could not gauge its legal implications without seeing it at play. The Arizona law allows police officers [in the process of enforcing other laws] to check the immigration status of people they reasonably believe to be in the country illegally – a key part of the broader symbolism of state immigration laws intended to push illegal immigrants to move elsewhere.
That spectre of “racial profiling” is a critical one as attitudes around immigration are looming larger in the presidential election.