In 1989, San Francisco passed the “City and County of Refuge” Ordinance (also known as the Sanctuary Ordinance) which prohibits City employees from helping Immigration and Customs Enforcement (ICE) with immigration investigations or arrests unless such help is required by federal or state law or a warrant. . . . In providing such assistance, faith communities were responding to the difficulties immigrants faced in obtaining refugee status from the U.S. government. Municipalities across the country followed suit by adopting sanctuary ordinances.
In recent years, the Sanctuary Movement has experienced a rebirth, as grassroots organizations, faith communities, and local government have stood firmly against repressive immigration proposals in Congress and immigration raids that separate families. In February 2007, Mayor Gavin Newsom reaffirmed San Francisco’s commitment to immigrant communities by issuing an Executive Order that called on City departments to develop protocol and training on the Sanctuary Ordinance.” (http://sfgsa.org/index.aspx?page=1067)
The Sanctuary Ordinance does NOT apply to persons who commit certain crimes.
“Nothing in this Chapter shall prohibit, or be construed as prohibiting, a law enforcement officer from identifying and reporting any person pursuant to State or federal law or regulation who is in custody  after being booked for the alleged commission of a felony and is suspected of violating the civil provisions of the immigration laws . . . [OR] . . . .  who has previously been convicted of a felony committed in violation of the laws of the State of California”. (SEC. 12H.2-1.)