"We want to send a message," Supervisor David Campos told a rally on the steps of City Hall this morning. "There are consequences when you target a whole people."

Last Friday, Arizona Gov. Jan Brewer signed a law making it a crime for an immigrant to be in the state without proof of legal residency and requiring police to seek out and detain anyone suspected of being in the country illegally.

The law, which will take effect this summer, is certain to face legal challenges. President Obama has called the bill "misguided" and ordered the Justice Department to determine whether it violates civil rights.

There's no way to tell yet how a boycott of Arizona would affect San Francisco.

"We're trying to figure that out now," Campos said. "We do know that we won't be sending any city employees to conferences in Arizona."

City Attorney Dennis Herrera also called for a wide-ranging boycott of Arizona and pledged to have attorneys in his office work with the city to identify contracts with Arizona companies and help break those contracts where possible.

The boycott resolution won't be the only immigration-based measure on the board's agenda Tuesday. The supervisors also are expected to pass a resolution condemning audits by the Immigration and Customs Enforcement designed to force local employers to fire undocumented workers.

The resolution calls for Congress to place a moratorium on "piecemeal" immigration enforcement efforts and encourages Congress and the president to pass a comprehensive immigration reform bill "that prioritizes keeping families together, upholding civil and human rights and promoting economic justice."

E-mail John Wildermuth at jwildermuth@sfchronicle.com