How Many Illegal Aliens Reside in Sanctuary Jurisdictions?

When President Trump begins his efforts to deport illegal immigrants in January, he will need to overcome “sanctuary jurisdictions” that do not fully cooperate with Immigration and Customs Enforcement (ICE). As my colleague Jessica Vaughan explains, sanctuary jurisdictions are state or local governments that frustrate enforcement by “refusing to or prohibiting agencies from complying with ICE detainers, imposing unreasonable conditions on detainer acceptance, denying ICE access to interview incarcerated aliens, or otherwise impeding communication or information exchanges between their personnel and federal immigration officers.”

To assess how much of an obstacle to enforcement these sanctuary jurisdictions are, we first need an estimate of how many illegal immigrants reside in them. The table below combines the Center’s list of sanctuary jurisdictions with our illegal immigrant population estimates. Although there is much imprecision in the data, the bottom line is that close to eight million illegal aliens, equaling 56 percent of the estimated nationwide total, live in sanctuary jurisdictions.

As Table 1 indicates, 13 states plus D.C. impose statewide sanctuary rules. These states harbor 45 percent of the nation’s illegal immigrants, accounting for the vast majority of those in sanctuary jurisdictions. California stands out with three million illegal immigrants, or 21.8 percent of the nationwide total.

A further three states do not have state-level rules but have so many local sanctuary jurisdictions that they are treated as full sanctuary states in this analysis. About 751,000 (or 5.4 percent) of the nation’s illegal immigrants find sanctuary in those states.

Another 822,000 (5.9 percent) live in sanctuary localities within non-sanctuary states. There are dozens of these localities ranging in size from major metropolitan centers (such as Atlanta) to small counties in rural areas.

Enforcement-minded states need not tolerate local sanctuaries, as the high-immigration states of Texas and Florida already demonstrate. Those two states have no local sanctuaries because they ban them statewide. Every state should follow their lead. Eliminating sanctuaries is one of the most important steps that states can take to assist the Trump administration with enforcement.

Methodological Notes

To estimate the number of illegal immigrants across sanctuary states and localities, we first turn to our previous analysis of the illegal immigrant population in the American Community Survey (ACS). This analysis predates the Biden surge. However, we use it here only to establish the share of illegal immigrants who live in each sanctuary jurisdiction. We then multiply those shares by the Center’s latest estimate of the total illegal population in the U.S., which is 14 million.

Estimates of both the number and distribution of illegal immigrants are subject to significant uncertainty. The 14 million estimate assumes that the Census Bureau misses about the same share of illegal immigrants as it did prior to the Biden surge. If the rate of undercount has since increased, then the actual number of illegal immigrants will be greater. As for the distribution of the 14 million, we had to omit many of the low-population sanctuary jurisdictions from the analysis because they cannot be identified in the ACS public-use data. These jurisdictions are so small, however, that they collectively could add only a few percentage points at most to our 56 percent estimate, and their omission may cancel out small overestimates elsewhere.