Tension between the federal government and so called “sanctuary” cities, counties, and states has been rising, with President Trump threatening to withhold millions of dollars in federal funding for law enforcement programs to those states. No place is this tension more apparent than in California. In March, Attorney General Sessions put pressure on the state when he filed a lawsuit charging that California has violated the Constitution with laws that adversely impact the work of federal immigration officers—a charge that California Governor Brown and AG Becerra refute. At the same time, U. S. Immigration and Customs Enforcement agency (ICE) enforcement is on the rise, with the number of arrests in 2017 reportedly up by 40 percent from the year before. Here, Lisa Weissman-Ward, clinical supervising attorney and lecturer in law with the Immigrants’ Rights Clinic at Stanford Law School, explains the legal challenges facing sanctuary states and cities—and undocumented residents living here.

First, can you give us a sense of the number of people affected by this? About how many undocumented immigrants live in the Bay Area?

We don’t have exact data on the number of undocumented individuals. Of the estimated 11 million undocumented individuals in the United States, approximately 7 million are living in mixed-status families, with authorized immigrants and undocumented members. So, it’s hard to estimate. The latest data from a 2010-2014 report tell us that there is a high percentage of mixed status families in the Bay Area. Here are some examples: 30% of residents in Alameda County are immigrant and/or undocumented, 23% in Contra Costa county, 20% Sacramento county, 34% San Francisco city and county, and 37% in Santa Clara county.