While policies intended to protect illegal immigrants from U.S. Immigration and Customs Enforcement officials have been implemented across the U.S., insiders on the front line of law enforcement in many "sanctuary cities" are still helping federal agents nab suspects.

What are the details?

According to The Associated Press, local police and other employees within sanctuary jurisdictions are assisting ICE agents a number of ways, despite laws prohibiting such cooperation.

Last month, it was discovered that staffers at the Bernalillo County Jail in Albuquerque, New Mexico, were granting immigration authorities access to its database and, at times, tipping off ICE regarding an inmate's release. When county commission chairwoman Maggie Hart Stebbins found out, she was "surprised and horrified" she told the AP.

"Individual employees do not have the freedom to pick and choose what they want to observe," she said.

Since Philadelphia became a sanctuary city, police have contacted ICE on 10 occasions upon the arrest of undocumented suspects, according to The Philadelphia Inquirer. In another instance, the city's own deputy managing director alerted the feds of five illegal immigrants who were being released from jail following their arrests for particularly heinous crimes (including the rape of a child and attempted murder). He later said he regretted the decision.

The AP reported similar examples of informal relationships between ICE and local police in Chicago, and in several California communities such as Orange County.

Anything else?

Sanctuary cities started cropping up in the 1970s starting with Berkeley, California. But immigration officials and other law enforcement officers have become increasingly outspoken against the policies in recent years, as hundreds of places across the U.S. have adopted laws limiting or refusing cooperation with ICE resulting in very real consequences.

The policies allowing criminal aliens safe harbor came under intense scrutiny in 2015 following the high-profile death of Kate Steinle, who was murdered in San Francisco by an illegal immigrant who had been deported several times but returned and enjoyed the protections of the city's sanctuary status.

Just this week, an illegal immigrant with multiple prior convictions was arrested in the stabbing death of a California woman, after Santa Clara County officials refused nine retainer requests from ICE to question the suspect because of their sanctuary city status.