Demonstrators confront each other, Friday, July 4, 2014, outside a U.S. Border Patrol station in Murrieta, Calif., over illegal immigration. (AP Photo/Mark J. Terrill)

San Francisco and other cities across the United States have created so-called “sanctuaries” for illegal aliens. These municipalities are defying federal immigration law, just like some Southern jurisdictions that defied federal civil rights laws in the 1960s.

But unlike that earlier era, today’s sanctuary cities are creating safe havens for known criminals. Their policies have victimized innocent Americans, enabling illegal aliens to commit thousands of crimes that would not otherwise have occurred.

There is no question that sanctuary policies violate federal immigration law. One provision of the law (8 USC 1373) bans local governments from preventing law enforcement or other government officials from sharing information with the federal government on the “citizenship or immigration status, lawful or unlawful, of any individual.”

So sanctuary policies such as those in San Francisco that ban local police officers from notifying the Department of Homeland Security when they arrest a criminal alien—or release him after he has served his sentence—are plainly illegal. Unfortunately, in keeping with its general non-enforcement policy regarding immigration law, the Obama administration announced in 2010 that it would not sue sanctuary cities for flouting the law.

We know these criminal aliens are victimizing Americans. In 2011, the Government Accountability Office released a study on approximately 250,000 illegal aliens locked up in our federal, state, and local prisons. Those prisoners had been arrested nearly 1.7 million times and committed 3 million offenses, averaging about seven arrests and 12 offenses each. Their convictions ran the gamut from drug-dealing and sex crimes to kidnapping and murder.

California, Texas, and Arizona, which have large numbers of illegal aliens, have significant problems due to those aliens breaking the law. Indeed, an unreleased internal report by the Texas Department of Public Safety indicates that from 2008 to 2014, illegal aliens committed over 600,000 crimes—including nearly 3,000 homicides and almost 8,000 sexual assaults—in that state alone. No wonder Texas is leading 26 states in a lawsuit against the federal government that has so far successfully blocked Obama from implementing his 2014 immigration amnesty plan.

When local jurisdictions protect illegal aliens from law enforcement, they enable them to commit more crimes. Kathryn Steinle, a 32-year-old resident of San Francisco, would be alive today but for that city’s sanctuary policy. On July 1, she was murdered by an illegal alien who had previously committed seven felonies. The man who shot her in the back, Juan Francisco Lopez-Sanchez, had been released from custody by San Francisco after city officials decided not to prosecute him on a drug charge. They did not hand him over to U.S. Immigration and Customs Enforcement, even though the agency had filed an immigration detainer on him. Lopez-Sanchez stated in an interview that “he knew San Francisco was a sanctuary city where he would not be pursued by immigration officials.”

It was an all too familiar story. In 2008, an illegal alien gang member murdered a father and his two teenage sons as they returned to their San Francisco home from a family barbecue. The killer had been convicted of two violent felonies as a juvenile: a gang-related assault and the attempted robbery of a pregnant woman. But because San Francisco’s policy is to ignore immigration status, federal authorities were never informed that the two-time felon was in the country illegally.

Every day, thousands of innocent Americans are victimized by sanctuary policies that allow dangerous predators to roam their cities. Local officials are putting the welfare of criminals who have no right to be in our country above the welfare of their law-abiding citizens. These policies must be changed.

If the politicians running those cities won’t do so, perhaps the next administration will direct the Justice Department to enforce U.S. law and force them to change these dangerous policies.

Originally published in The Washington Times.

Hans von Spakovsky is an authority on a wide range of issues—including civil rights, civil justice, the First Amendment, immigration, the rule of law and government reform—as a senior legal fellow in The Heritage Foundation’s Edwin Meese III Center for Legal and Judicial Studies and manager of the think tank’s Election Law Reform Initiative.