By Pat Toomey

For more than a year, I have warned about the dangers posed by sanctuary cities. Sadly, Philadelphia keeps proving me right - at the terrible expense of our children and public safety.

Just before Thanksgiving, federal law enforcement officers ended a year-long search for Winston Enrique Perez Pilarte, a 40-year-old illegal immigrant from the Dominican Republic. In July 2015, Philly police arrested him for child rape. Pilarte was a known danger; he had previously been convicted of drug trafficking, resisting arrest, and theft. So when Pilarte raised the funds for bail in November 2015, federal law enforcement officers asked Philadelphia to hold him temporarily so they could pick him up and begin deportation proceedings. But the city refused and, instead, released this dangerous man onto the streets of Philadelphia, where he roamed free for a full year.

Shockingly, Pilarte is not the only child rapist the city has released.

In 2015, Philadelphia had Ramon Aguirre-Ochoa in custody on charges of aggravated assault, making a terroristic threat, and harassment. Aguirre-Ochoa is an illegal immigrant from Honduras who was deported in 2009, but illegally re-entered the United States. Federal law enforcement officers asked the city to hold him temporarily so they could apprehend and deport him. But, again, the city refused and released him. The result? In July, Aguirre-Ochoa was arrested again, this time for raping a small child.

Why does Philadelphia keep releasing dangerous criminals? Because Philadelphia is a "sanctuary city" - a jurisdiction that forbids its local police from cooperating with federal immigration officers.

Sanctuary-city policies have been criticized by officials from both political parties - including former Pennsylvania governor and lifelong Democrat Ed Rendell, President Obama's secretary of Homeland Security Jeh Johnson, and dozens of law enforcement officers across Pennsylvania. I was proud that the legislation I introduced - the Stop Dangerous Sanctuary Cities Act - was supported by a bipartisan majority when the U.S. Senate voted on it last year. Unfortunately, a minority of my colleagues filibustered, blocking a final vote on the bill.

Perhaps this bipartisan opposition to sanctuary cities is why defenders of the policy often dodge the facts and instead try to confuse the issue.

For example, some proponents of sanctuary cities blame federal law enforcement. The U.S. Constitution, they assert, requires a judicial warrant for police to hold someone. If federal officers get a court-issued warrant, they say, sanctuary cities will cooperate.

This is absurd on its face. If the Constitution required a warrant for every arrest, police could never stop a suspect fleeing the scene of a crime or arrest someone they witness assaulting another person. Police would have to go to a judge, get a warrant, and hope the suspect was still there, waiting to be taken in, when they returned.

Philadelphia's sanctuary city policy is so extreme that, even if federal officials obtained judicial warrants for dangerous, illegal immigrants, police are still constrained from cooperating with federal immigration officials. Philly's policy states that local police may not share information with federal immigration officials or temporarily hold an illegal immigrant unless (1) federal officials have a warrant, and (2) the illegal immigrant has already been convicted of a first- or second-degree violent felony. Thus, even when federal officials have a court-issued warrant, local police may not be allowed to cooperate.

The case of Jose Palermo-Ramirez, a third child molester released by the city, illustrates the point. The 43-year-old illegal immigrant was convicted of indecent assault on a 7-year-old girl. Because Palermo-Ramirez's crime constituted a third-degree felony - not a first- or second-degree felony as required by the city's policy - Philly police were not allowed to notify immigration officials when Palermo-Ramirez finished serving his time. Instead, they were forced to release this convicted child molester onto the streets. This is intolerable.

Finally, some argue that cracking down on sanctuary cities will make us less safe, by discouraging crime victims and witnesses from coming forward for fear of being deported. But my legislation would create a special exemption that allows a jurisdiction to refuse to cooperate for crime victims and witnesses and not lose any federal funds.

And my legislation is endorsed by four national law enforcement groups - including the National Association of Sheriffs - along with dozens of local law enforcement officers in Pennsylvania. These officers would not support a bill that makes our communities less safe.

The reality is that our law enforcement officers on the ground know the facts. They know that sanctuary cities pose a serious public safety risk. They know that the people of Pennsylvania, especially our children, deserve better. They know that it is past time to end dangerous sanctuary city policies. As your senator, I will continue leading the charge to do so, and to keep our children and our communities safe from dangerous sanctuary city policies.

Pat Toomey is a Republican U.S. senator from Pennsylvania. @SenToomey