Amid much anticipation, the U.S. Supreme Court issued its long-awaited ruling on Arizona’s controversial immigration law, SB 1070. Surprising some observers, the court ruled by a 5-3 majority that states may not attempt to supplement federal immigration law with rules of their own. The ruling is largely a victory for agriculture and other proponents of comprehensive immigration reform, who oppose the creation of immigration laws at the state and local levels.

SB 1070 had four major provisions, and three were struck down. First, the court ruled that Arizona cannot make it a state crime to be an illegal immigrant or to not carry proof of legal immigration status, because that would contradict existing federal law. Second, the court also ruled, for the same reason, that Arizona cannot make it a state crime for illegal immigrants to seek employment. Third, a provision was also struck down that allowed law enforcement to arrest legal immigrants if they believe there was probable cause the person committed a deportable offense.

What was upheld? The court did let stand, for now, a provision allowing police to check the immigration status of individuals stopped for other reasons if there is probable cause to believe the person is an illegal immigrant. However, many observers said that the court, in its ruling, signalled that it would reserve judgment on this type of provision until it sees how Arizona, and potentially other like-minded states, pursue enforcement.

You can download and read the full text of the court’s ruling in Arizona et al v. United States (2012) (PDF). Scotusblog breaks down the ruling in very clear terms here.

The ruling was written by Justice Anthony Kennedy, whom court-watchers consider the court’s main moderate swing vote. Joining him in support were Chief Justice John Roberts and justices Stephen Breyer, Sonia Sotomayor and Ruth Bader Ginsburg. Roberts is considered conservative, while the other three are considered liberal. Judge Antonin Scalia wrote a dissenting opinion on behalf of the court’s other conservative members, who include justices Clarence Thomas and Samuel Alito. Justice Elena Kagan did not participate in the case because of her prior involvement in it. Before taking the bench, she worked for the Obama administration as solicitor general.