The mayor of Philadelphia, Jim Kenney, reminded everybody this past week that his stand to keep our city a place where immigrants can feel safe is based on a principle enshrined in the 4th Amendment of our Constitution.

This amendment simply says that the “right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated.”

“No warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized,” says the 4th Amendment, proposed here in Philadelphia in 1789 by James Madison, our 4th President, and the Father of the Bill of Rights.

The principle that survives to our days is the best defense against the renewed threats of federal government action against cities that harbor immigrants.

This past Sunday the chief of staff of the new President-Elect Donald Trump, Reince Priebus, said that the new administration is is “looking into” cutting millions of funding to so-called sanctuary cities on Day 1 of Trump’s presidency.

Priebus implied that cities can’t have it both ways: ignore federal law, and then ask for federal money.

It is not compliance of federal law, but the observance of a Constitutional principle that amply supersedes it, in the new context Mayor Kenney has timely placed the discussion.

He is not alone in this national debate. From New York to Los Angeles, where Mayors Eric Garcetti and Bill de Blasio have defended their right to preserve their cities friendly to immigrants, there are  300 others jurisdictions across the U.S. identified as “sanctuary cities.”

Chicago Mayor Rahm Emanuel, for example, has said in clear terms that his city “is and will remain a sanctuary city.”

The Mayor of New York, Bill de Blasio, went further to say that its government is “not going to sacrifice a half million people who live among us, who are part of our community,” referring to an estimate of the number of unauthorized immigrants living in New York. “We are not going to tear families apart,” de Blasio said.

A handful of other mayors of large cities have been equally outspoken in the subject, among them, Oakland, CA; Minneapolis, MN; San Francisco, CA; and Seattle, WA.

By invoking a Constitutional amendment the Mayor of Philadelphia has gone farther than any of them by connecting his policy to a Constitutional principle.

"We have no authority to violate the Fourth Amendment,” said Kenney last week.

In a very opportune time, our Mayor has taken a leadership position among its peers and has put our city in the center of a national conversation likely to take place as soon as the new President is sworn in.