"Our failure to act responsibly at the federal level will only open the door to irresponsibility by others," Obama said in the Rose Garden ceremony. "That includes, for example, the recent efforts in Arizona, which threaten to undermine basic notions of fairness that we cherish as Americans, as well as the trust between police and our communities that is so crucial to keeping us safe."
Obama has devoted more energy to passing an immigration bill this year, but the prospects remain dim, with only one Republican senator voicing measured support and some Democrats hoping it gets put off.
In Arizona, officials said they acted because the federal government had failed to secure their border with Mexico, making the state vulnerable to drug traffickers and human smugglers who are blamed in the killing of a rancher on his land in southern Arizona last month.
Secretary of Homeland Security Janet Napolitano, Brewer's predecessor, said the law would hinder federal law enforcement efforts in the state.
"With the strong support of state and local law enforcement, I vetoed several similar pieces of legislation as governor of Arizona because they would have diverted critical law enforcement resources from the most serious threats to public safety and undermined the vital trust between local jurisdictions and the communities they serve," she said in a statement.
State Sen. Russell Pearce, who wrote the legislation, scoffed at Obama's opposition, contending that the president stood "against law enforcement, our citizens and the rule of law."
Gutierrez said Obama's statements heartened activists who were angered by recent federal immigration raids and the lack of an immigration bill in Washington. "People were beginning to feel mighty abandoned by the administration," he said, "and that helped calm it."
nicholas.riccardi@latimes.com
Times staff writer Richard Serrano and Peter Nicholas in the Washington bureau contributed to this report.
