During his campaign, President-elect Trump’s most consistent policy position was support for harsh immigration enforcement policies, including mass deportation of unlawful immigrants. Troublingly, government identity databases created for other purposes, many of them noble, could significantly increase the effectiveness of a Trump deportation scheme. The frightening specter of the federal government using applications for Deferred Action for Childhood Arrivals to target young unlawful immigrants would be a humanitarian and economic disaster.

President Obama’s 2012 DACA executive order granted a temporary renewable work permit and protection from deportation to some unlawful immigrants brought here as children. About 665,000 signed up for it, allowing them to work legally for the first time in their lives. The problem, however, is that this executive action could be overturned by the next president.

Trump has promised to do that on his first day.

Ending DACA is bad enough. The bigger danger is that these unlawful immigrants had to give their names, addresses and other personal information to the federal government in order to obtain DACA in the first place. The government will still have all of that identity information even if DACA is repealed. The personal information of DACA recipients solves the hardest problem of deporting illegal immigrants: Identifying and finding them.

About 850,000 New Yorkers have the city’s IDNYC card. Most of them are unlawful immigrants. The card was supposed to make working and living in the city easier, but it also centralized the addresses, names and other information of many unlawful immigrants in an encrypted NYC database. New York Mayor Bill de Blasio suggested the day after Trump’s election the database could be “scrubbed” to protect the individuals in it.

What is he waiting for?

This should produce deja vu. Politically unpopular and minority communities have long had good reason to fear government registration efforts. In the 1950s, the state of Alabama tried to force the NAACP to turn its membership lists over to the government. The NAACP refused, and eventually won in the Supreme Court. The court cited “the vital relationship between freedom to associate and privacy in one’s associations,” when it ruled that revealing the NAACP’s membership lists would impermissibly infringe on the members’ constitutional rights.

The war on terror has created similar registration fears in the Muslim community, which has been subjected to extensive surveillance and data basing efforts. A spokesman for Trump’s super PAC actually claimed Wednesday there is a “precedent” for a registry of Muslim immigrants, referencing Japanese-American internment camps. More recently, due-process-free no-fly lists and a fruitless effort to “map” the New York Muslim community have harmed them most of all, but others have also been affected, including the late Sen. Ted Kennedy, D‑Mass.

Americans are added to these lists by government “nominators.” Those added do not receive a hearing, access to evidence or the opportunity to challenge their accusers. It is, in short, simply a registry of (predominantly Muslim) Americans according to the whims of government bureaucrats. This list could be used to enforce laws that wreak havoc on civil liberties but haven’t been written yet.

Earlier this year, gun control advocates and national security hawks attempted to ban anyone on the no-fly list from buying firearms. The effort failed, but the rhetorical push for it was intense. Sen. Joe Manchin, D‑W.Va., even declared that affording due process to people on the registry was “killing us.”

Gun rights advocates have pushed against registries longer and harder than any other group. A national database of gun owners is the deepest line in the sand for 2nd Amendment advocates. Such a registry would be a necessary prerequisite of a potential national confiscation program like the one used in Australia in the 1990s. The lack of a registry is a necessary precaution because it dooms confiscation to failure.

Supporters of gun control routinely disclaim any interest in the creation of such a registry and current federal law forbids such registries, though the government sometimes cheats. Many common gun control proposals, such as universal background checks, can’t function without a registry. If the government doesn’t know who owns which guns initially, it can’t prove whether illegal exchanges have occurred.

Gun rights advocates are often mocked for fearing the misuse of registry information. “Nobody is coming for your guns,” they say. “What are you so afraid of?”

We’re afraid of the same things the DACA recipients are now afraid of, and what prompted de Blasio to suggest scrubbing government databases.

The mere possibility of this threat should be a rebuttal to all those who mock the paranoia of gun-registration advocates. Government registries of vulnerable communities are always only one election away from being abused.

Ideally, these registries wouldn’t exist in the first place. Insofar as they do, they should be destroyed.