Attorney General Jeff Sessions’s recent threat to pull grants from “sanctuary cities” should come as no surprise to those who spent any time listening to the rhetoric of then-candidate Donald Trump on the campaign trail. Doing so, you might have thought that a very disproportionate number of America’s problems are caused by “illegal immigrants”—people who lack the legal qualifications to live and work in this country. It is to remedy this apparent problem that President Trump wants to increase immigration enforcement and build a wall on the southern border of the United States. Even if we put aside the enormous price tag to build and man a border wall of that size and the logistical nightmare required to successfully identify, detain, and deport the estimated 11 million undocumented immigrants in this country, these laws will not likely fix the problems they are meant to solve. Indeed, history shows that increased immigration enforcement and other measures meant to discourage immigration have unintended consequences that can actually increase the number of undocumented immigrants and decrease overall public safety.

Take, for example, the border wall. What walls the United States already has on its southern border were built to keep unauthorized people out of the country, and Trump’s proposed expansion will, according to him, be better than what we have now. But as Douglas Massey noted in 2015, when the current walls and enforcement militarized the border in the 1980s and ’90s, it disrupted decades of “circular” migration. Before the buildup, Mexican migrants would typically come to the United States to work and then return home voluntarily, so at any given time the “illegal” population was relatively small. However, by making the trip across the border more difficult—and thus more expensive and dangerous for unauthorized persons—more migrants stayed in the United States. In effect, the current walls have been much better at keeping unauthorized immigrants in the United States than it has at keeping them out.

And as my colleague Alex Nowrasteh has written, a large reason we have so many unauthorized immigrants in the first place is that the government shut down programs that allowed people to come and work legally. Among these was the Bracero program that allowed seasonal migration for labor:

From 1942 to 1964, nearly five million Mexican workers legally entered and worked in the United States on Bracero, returning home at the end of their seasonal employment. At the height of the program, half a million workers came in annually to work on American farms. In its main failing as a bill, the 1965 Act did not create a similarly flexible migrant work visa and also piled on more wage regulations for the few economic migrants allowed, consigning these migrants to work as illegal immigrants.

Bracero was not without its flaws, but the fact remains that when given legal means to make money in the United States, immigrants took advantage and played by the rules. Our current laws, on the other hand, prevent most unskilled immigrants from coming here legally and don’t allow those already here to “go to the back of the line” to do so. Our current system is incapable of meeting the labor demands of the American economy, and the laws of economics usually trump the laws of Congress. Thus, millions of good, hardworking people live in the shadows in violation of inapt, antiquated laws so that they can make a living and keep the American economy going.

Some of the sensationalist rhetoric around undocumented immigrants has also focused on crime and violence, very often on rare and horrific acts of violence caused by individuals here illegally. But a wide range of data show that increased violent crime rates are not correlated with increased immigration and, indeed, may be inversely correlated. In plain English, an increase in immigrant populations does not result in crime increases and, in many cases, may result in crime rate declines. Almost all available data show that immigrants are less likely to commit crimes than native-born Americans, and violent crimes in particular. Although no one can be sure exactly why these data show this, it makes intuitive sense that people who self-select to leave their loved ones to find work in a new country would be less likely to violate the laws and norms that would jeopardize the opportunities they sacrificed so much for.

Again, however, certain federal law enforcement practices undermine the principles they are supposedly there to uphold. In recent weeks, federal immigration officials have seized or prepared to seize people at courthouses who may be in violation of immigration laws. Perhaps the most famous case came from El Paso, Texas when federal agents detained a woman who was filing a protective order against a domestic abuser. Some people close to the case believe the woman’s abuser was the person who tipped off federal authorities to her court appearance.

Since the El Paso case, court watchers and lawyers have noticed that domestic violence and sexual assault complaints are measurably down in Latino areas in cities like Los Angeles and Denver. Crime victims who fear deportation—or perhaps deportation of innocent loved ones—are reluctant or unwilling to come forward to identify their abusers. This chilling effect most directly harms the victims of crimes, not the perpetrators, who may not even themselves be immigrants.

Police officers cannot do their jobs effectively without cooperation from victims, witnesses, and other members of the general public. One detective complained to the Los Angeles Times that “I can’t get justice for people, because all of a sudden, I’m losing my witnesses or my victims because they’re afraid that talking to me is going to lead to them getting deported.” Nevertheless, immigration authorities continue to subvert the priorities of local law enforcement, including posing as local police officers to gain entry into immigrants’ homes, which law enforcement officials called “corrosive…to public safety.”

According to an internal memorandum, the Trump Administration has explored lowering hiring standards for agents to dramatically increase staffing at Border Patrol and the U.S. Customs and Border Protection (CBP). If history is a guide, lower standards will lead to increased problems of misconduct and corruption, due to the intense pressure to smuggle drugs, guns, money, and people across the American border, often with the assistance of bribed or otherwise compromised agents. Jay Ahern, a deputy commissioner of CBP in the George W. Bush Administration, told Foreign Policy, “We actually lived through this…If you start lowering standards, the organization pays for it for the next decade, two, or three.” The federal government has released studies that indicate the highest incidents of misconduct and corruption in CBP happen at the southwestern U.S. border. More people on guard does not necessarily mean better border security.

Federal immigration enforcement policy has been working at cross-purposes with its stated goals for decades, and the Trump Administration seems dedicated to the most counter-productive policies to those ends. The walls and laws that were created to keep people out have kept far more undocumented people in the country than there had been in years past. Trump wants more laws and walls. Yet the overzealous tactics to target victims of crimes for possible deportation poison the relationship between local police and those they are sworn to protect and serve, allowing more crime to happen and more violent criminals to escape justice. Trump’s Department of Justice is pushing the envelope of aggressive enforcement. And to implement a hasty increase of immigration officials on the border would be to repeat a recent mistake that could lead to more problems of bribery, smuggling, and corruption among federal law enforcement, thus diminishing border security. Trump appears to be pushing for quantity at the very high price of officer quality.

Would it be too much to ask to make immigration policy sane again?