The law requires immigrants to carry their alien registration documents at all times and requires police to question people if there is reason to suspect they're in the United States illegally.

CNN: Arizona students speak out on immigration law

Despite erroneous and misleading statements suggesting otherwise, the new state misdemeanor crime of willful failure to complete or carry an alien registration document is adopted verbatim from the same offense found in federal statute.

CNN: Immigration excerpts: Obama vs. Brewer

Justice Samuel Alito agreed with the majority that Arizona's alien-registration requirement was void, but voted to uphold SB 1070 provisions making it a crime for illegal immigrants to seek work and authorizing warrantless arrests of certain aliens.

WSJ: Supreme Court Splits on Arizona Immigration Law