In 2015, New York City launched a municipal identification program with the goal of giving some of the city’s most vulnerable residents access to services that require an ID. Mayor Bill de Blasio gave the plan vocal support, saying the card represented “who we are: New Yorkers who value equality, opportunity, and diversity.”

A Trump presidency will raise new questions about the database

But now parts of the program are suddenly being questioned. As an unexpected Donald Trump term approaches, de Blasio last week suggested the city would fight to prevent the future president from accessing ID-related data, which contains personal information on undocumented immigrants.

The hurdle is one of many that cities will face as they prepare for an administration that, at least by its own account, will use every tool it has to target undocumented immigrants. In an interview aired Sunday, Trump vowed to deport millions — raising questions about where the president-elect will look for them. In some cases, such as municipal ID programs, data collected to improve the lives of immigrants may be in danger of being used for a very different purpose.

"So on something like [the ID database], I think because it touches that button directly of whether people's personal privacy is going to be respected,” de Blasio said in a press conference. “I think that's one where there would be a real fight."

“I think that's one where there would be a real fight."

When the city began issuing IDNYC cards, it did so to provide identification for residents who might not have other options. The ID is accepted at several banks and credit unions, and it provides identification for trans residents who want their gender identity affirmed.

But in the process, New York created a database of ID holders. Although the database does not specify immigration status, a considerable share of residents who signed up for the program were immigrants. Trump has not himself made any statements about such data, but his rhetoric suggests the information may face a danger it hasn’t before.

Other cities have grappled with their databases

New York was not the first city to establish a municipal ID, and other cities have grappled with how to handle data collected on marginalized communities by these programs. In New Haven, Connecticut, where another ID system is in place, anti-immigrant groups tried to get information on cardholders through a public records request, an action which the city successfully fought.

In San Francisco, the city doesn’t retain data from documents it receives for its ID program, heading off any attempts to obtain it.

“San Francisco actually foresaw this concern and went to great lengths to create its municipal IDs without saving the data,” says Julia Harumi Mass, a senior staff attorney at the ACLU of Northern California, which defended the ID against a legal challenge.

New York was warned of the problems that might arise when it first enacted the IDNYC plan. As far back as October 2014, immigration advocates were questioning the unintended consequences that could result from retaining the underlying information on cardholders — whether it would be a way for immigration officials to target undocumented immigrants, or even whether the federal government might exercise laws like the Patriot Act to obtain it.

Immigration advocates expressed concerns about New York’s data

But the city opted for a system that retains underlying documents, with provisions that destroyed them after two years. It did, however, contain a kill switch: the city can prevent law enforcement use by changing how the data is stored, including by deleting it. A councilman said in 2015 that the kill switch was “in case a Tea Party Republican comes into office” — but now the option, which also goes into effect if the city takes no action, is under closer consideration.

A spokesperson for the mayor’s office told The Verge that the city will take any necessary measures to protect cardholders’ confidentiality, and said it would only provide access if a cardholder agrees, if another city agency needs the information for other programs, or if a court orders the information to be released.

So far, requests made to the database have been relatively few. In the last quarter, according to the most recent quarterly report on the program, IDNYC information was disclosed for two applicants, after the city was provided a subpoena. (It also said it denied an insufficient request from the NYPD.)

So far, there have been few requests for the data

“Under the local legislation for the IDNYC program, local law enforcement officials must provide a judicial warrant or judicial subpoena to obtain applicant information,” the city explains in a privacy FAQ on the data. “This means a judge must have approved the request for information.” The information is stored on encrypted servers, and, within legal parameters, the city says it attempts to notify anyone whose information is targeted by law enforcement.

Still, the data is out there, and because of a decision made well before the prospect of a Trump presidency seemed real, the mayor must consider that an administration with a far more hostile view toward immigrants will soon be in power.

The law gives the city until the last day of 2016 to “make any appropriate modifications to the policy for retention of records related to the New York city identity card program.” With Trump’s inauguration set for January 20th, the city will have to decide soon.