Let's start with a simple fact: No foreigner has a right to visit or settle in the United States without permission from the federal government. No governor, no mayor, no "welcoming" sanctuary city can grant "permission" to stay. "Protecting" those here illegally undermines U.S. law and is dangerous.

First, it creates disrespect for law. Second, criminals and terrorists are among those who come here illegally. Five of the 9/11 mass murderers had overstayed their visas.

Immigrants, both legal and illegal, have lower crime rates than the native born, but they do commit crimes. Of the 11 million people estimated by the New York Times to be here illegally, the newspaper reported, 820,000 have been convicted of a crime — 300,000 of a felony. Those are not insignificant  numbers. There are many more.

A recent column of mine focused on a child rapist enabled by Philadelphia. The column listed eight other foreign felons in Philly.

When Immigration and Customs Enforcement, a division of the Department of Homeland Security, removes an undocumented foreigner, it is enforcing U.S. law. ICE staffers are amazed and hurt when people call them Nazis, as some protesters did in Portland, Ore., in July.

"It's offensive," says Simona L. Flores, director of ICE's enforcement and removal operations in the Philadelphia office, and a 30-year veteran of federal immigration enforcement.

"We try to enforce the laws as humanely and professionally as possible," says David O'Neill, assistant field office director.

It's not just the loony left. Some Trump wingnuts believe the FBI is a cancer. We are spitting on our sworn protectors.

Flores, who is new to Philadelphia, was surprised by what she calls a "lack of cooperation from the mayor's office."

Until recently, Philadelphia did cooperate, although minimally, by allowing ICE access to the Preliminary Arraignment Reporting System, which is how Philadelphia logs information about people arrested. Mayor Kenney canceled the access, putting ordinary Philadelphians at risk by shielding convicted foreign felons from deportation.

Whatever the good intentions, sanctuary cities such as Philadelphia thwart federal law, and misguided Democratic leaders gloat about it. Or do infantile celebratory dances.

One poll says that most Americans oppose sanctuary cities, which were criticized by then-Presidents Bill Clinton and Barack Obama. But nothing dents self-righteous Kenney's missionary zeal to shield lawbreakers.

ICE critics sometimes call it a "deportation force," but ICE also fights terrorism, as well as human and drug trafficking.

When ICE issues a detainer to get custody of a removable alien, Philly usually ignores it. The city can turn over prisoners if it wants to, but creates obstacles.

A 2016 Kenney executive order said the city would cooperate only with suspects convicted of first- and second-degree felonies that involve violence, but spokesman Mike Dunn says that is no longer operative. The city still deviously insists on a criminal warrant, knowing ICE can't get criminal warrants unless an immigration-related crime also has been committed, and that's usually not the case.

The previous stipulations were good news to Jose Palermos, convicted in 2013 of sexual assault on a 7-year-old girl, a third-degree felony. The city turned him loose instead of handing him to ICE for deportation. How can you defend that?

The city's criminal-warrant requirement is legally brilliant but morally bankrupt. Why does Philadelphia devote so much effort to noncitizens who don't belong here in the first place?

I asked the mayor's office for a one-paragraph justification of its sanctuary city policy.

I got several paragraphs, including the circular reasoning that not enforcing the law encourages immigrants to cooperate with law enforcement, but the nub is that "our policy affirms Philadelphia's place as a welcoming city open to all seeking the American Dream." Even those arriving illegally. Once you arrive, the city believes, you are immune from punishment.

The ICE managers I met with in their Center City office were mystified by walls erected by the city.

Those who would abolish ICE without replacing it with another agency with a similar mission would create open borders. And if we had open borders, we could be swamped by more than 150 million arrivals, according to a Gallup poll.

Those numbers would crack our economy like a walnut. How exactly would that improve America?