There are police. Just not members of the City of Chicago Police, though they are city employees that make $50-80k. It’s just that they do not have to meet the exact same standards as regular city police.
http://www.insurancejournal.com/news/midwest/2017/04/18/448039.htm
I think the question boils down to "Do they have the legal authority of police or not?"
I find it irritating that people will throw out smokescreens like "They are not the police, they are private security guards" and such.
If someone wants to make a point that hinges on a particular fact, they ought to make sure at least that the particular fact their point hinges upon is true.
I also find it unlikely that the "Aviation Police" won't have the legal authority to remove passengers designated as unwanted or disruptive. That would make no sense to me.