Governor Brewer signs Arizona SB 1070, the broadest state immigration law in US history at the time

Arizona Governor Jan Brewer signed Senate Bill 1070, the Support Our Law Enforcement and Safe Neighborhoods Act, making it a state crime for undocumented immigrants to be present without federal registration documents and requiring police to investigate immigration status during lawful stops when they suspected a violation. The law triggered immediate national controversy, with protests in over 70 cities and boycotts by companies, cities, and the six Mexican border-state governors. The Obama administration filed a federal lawsuit within months, arguing the law unconstitutionally usurped federal authority over immigration -- setting up the Supreme Court test that would define state immigration power for over a decade and directly shape the later Texas SB4 litigation.