Whether UVA’s findings are indicators of the policy’s success or troubling evidence of collateral damage depends on who you ask. For county supervisors, driving out legal immigrants and Hispanics was never a goal of the measure, but an “unintended consequence.” For others, this was a victory. From the report:

Some actors in the drama of the resolution’s passage had quite different goals. Some in the community who advocated the policy made clear…that they were hoping to “take back the County” by reversing the tide of rapid in-migration of Hispanics to Prince William County.

Immigration restrictionists also counted this as a win for “attrition through enforcement,” a strategy that calls for crafting harsh laws to make life so untenable for undocumented immigrants they choose to leave—an approach best described as “a product of delusion and cruelty.”

What about crime? After narrowing the policy’s focus to post-arrest status checks, county supervisors more explicitly aimed to improve public safety. According to the study, local immigration enforcement had no effect on “most types of serious and minor crime,” largely because undocumented immigrants commit a relatively small number of serious crimes. The study did, however, find a significant drop in aggravated assaults. In addition to reduced offenses, this decrease was attributed to reduced victimizations of undocumented immigrants as well as reduced crime reporting among them. Nor did these effects last very long.

Predictably, a recent Fox and Friends segment reduced the 300-plus page report’s meticulous and carefully qualified findings to one inaccurate headline: “Under Immigration Policy, Crime Drops.” This is despite the fact that one co-author said he had “no indication that the enforcement of the policy led to a reduction in crime.”

Should other localities follow Prince William’s approach to immigration enforcement? The authors conclude that their results should be only applied to other jurisdictions with “great caution.” They explain that the economic downturn combined with the “acrimonious and fear-inspiring” public discussion surrounding the policy may have had a lot to do with its’ effects. Moreover, these less-than-stellar results cost Prince William almost $3 million to implement. One author of the study advises would-be copycats: “This not a free policy…Don’t try this if you don’t want to spend some money.”

Nonetheless, a majority of county supervisors this week approved a policy statement saying that the county had implemented an “effective” immigration policy that should be used across the Commonwealth. Perhaps these supervisors didn’t read the entire report. UVA’s impressive and well-balanced study is a cautionary tale for localities looking to take immigration enforcement into their own hands.