President Donald Trump's executive order on immigration allows three-quarters of immigrants who entered the country illegally to be subject to deportation, according to The Center for Immigration Studies' Ronald Mortensen.

Trump's Executive Order 13768 "will not ‘exempt classes or categories of removable aliens from potential enforcement,'" unlike former President Barack Obama's immigration measures, writes Mortensen. "This means that the vast majority of people unlawfully in the United States are once again subject to deportation."

Trump addressed police officials Wednesday at the Major Cities Chiefs Association, where he asked for their aid in identifying and deporting illegal immigrants.

"I want you to turn in the bad ones," Trump said in his speech, according to Yahoo News.

"We're going to stop those drugs from poisoning our youth, from poisoning our people. We're going to be ruthless in that fight. We have no choice, and we're going to take that fight to the drug cartels and work to liberate our communities from their terrible grip of violence," he added, telling the audience to inform Homeland Security Secretary John Kelly "who the illegal immigrant gang members are."

"You have that power because you know them. You're there, you're local, you know the illegals, you know them by their first name, you know them by their nicknames. You have that power. The federal government can never be that precise, but you're in the neighborhoods. You know the bad ones. You know the good ones," Trump continued.

"So much of the problems — you look at Chicago and you look at other places — so many of the problems are caused by gang members, many of whom are not even legally in our country," he said.

Local police told CBS News in Chicago that they "have never linked the violence to an influx of illegal immigrants. Rather, they say, prison sentences for gun crimes are too lenient, allowing repeat offenders with gang ties out on the street to commit more violence."