Donald Trump yesterday announced a series of actions following up on the issue that animated his campaign: xenophobia. He signed one order to start building a wall on the Mexican border, and another that will make it easier to apprehend and deport immigrants in the U.S. and encourages retaliation against “sanctuary cities” that do not cooperate with federal immigration officials. He also reportedly intends to sign a third order that will bar Syrians and other refugees from “terror prone” nations from entering the United States. None of these policies is any more rational than his belief that votes from illegal immigrants caused his nearly 3 million-ballot loss in the popular vote, and none will be any more successful than the “major investigation” he promised into the fake vote fraud story.

First, the wall. Mr. Trump's Secretary of Homeland Security, John F. Kelly, said during his confirmation hearing this month that a “physical barrier will not do the job.” Rather, he said the key to protecting the southern border is maintaining effective partnerships with governments “as far south as Peru” to control the flow of drugs and migrants northward. The U.S. cannot succeed with “an endless series of ‘goal-line stands' on the one-foot line at the official ports of entry or along the thousands of miles of border between this country and Mexico,” he said.

But Mr. Trump's policies eschew such cooperation with neighbor governments and create conditions that will exacerbate the economic pressures that lead migrants to seek entry into the United States — whether by sneaking across the border, or, frequently, overstaying a visa. Mr. Trump has suggested that he will make good on his promise to get Mexico to pay for the wall by cutting off aid to that country. Currently, that's about $586 million a year, so depending on which estimate you believe for the wall's cost, we're talking about cutting off funds for 20 to 35 years, and since the lion's share of that is economic aid, he will only succeed in strengthening the impetus for Mexicans to enter the U.S. illegally. Ditto for his plan to tear up the North American Free Trade Agreement.

As for Mr. Trump's notion that we're under imminent threat from Syrian refugees resettling in the U.S. or from immigrants from Muslim nations, it's worth noting a few facts. A Cato Institute researcher crunched the numbers this fall and found that the odds of being killed in a terrorist attack perpetrated by immigrants in a given year are about 1 in 3.6 million, and the only reason it's anywhere near that high is the Sept. 11 attacks, which account for 98.6 percent of the deaths in the years studied. The odds of being killed by refugee, in particular? One in 3.6 billion. That's largely because refugees, particularly those from war-torn places like Syria, are already subject to what Mr. Trump likes to call “extreme vetting.”

Finally, Mr. Trump is precisely wrong that “sanctuary city” policies make Americans less safe. He has made an issue of a handful of cases in which Americans were killed by illegal immigrants to make his point, though the precise connection between those crimes and local policies relating to detaining people at the request of Immigration and Customs Enforcement officials is at best unclear. What is clear, though, is that dragooning local police into enforcing federal immigration law makes immigrants less likely to cooperate with police. Montgomery County Police Chief J. Thomas Manger, speaking on behalf of the Major Cities Chiefs Association, told a Senate panel in 2009 that “It's tremendously challenging to deliver police service to a community of people who are afraid to have any contact with the police. The results are an increase in unreported crime, reluctant victims and witnesses, and the targeting of immigrants by criminals, because the bad guys know that many immigrants will not call the police.”

Moreover, Mr. Trump's plan to withhold grant funds from sanctuary jurisdictions is almost certainly unconstitutional. Just as the principles of federalism laid out in the 10th Amendment prevented Congress from taking away existing Medicaid funds from states that refused to expand the program under the Affordable Care Act, Mr. Trump can't cut off grant money from local jurisdictions that choose not to enforce federal immigration law.

We would be among the first to agree that America's immigration system needs reform, but that's not what Mr. Trump is offering. Rather, he's serving up a healthy dose of scapegoating that will no more make this country safer and richer than it will give him the popular vote lead.