You may as well just tell them they are free to go be illegal immigrants in the country in violation of the law with zero expectation of punishment.
Well, yeah. It's a misdemeanor. These aren't violent felons.
Now you can prioritize, as Obama did, arresting violent criminals, drug smugglers, the people you actually want to keep out of this country.
Or you could jail everyone regardless of their situation, leading to a breakdown of social services that leads to government sanctioned child abuse.
These centers existed before Trump - that is true. A kid was supposed to be held there for a day or two until they could figure out housing with family or social services. They were not designed to process this many children at once. Now you have the government erecting tent cities in 100 degree heat holding anyone from infants to teenagers, for weeks if not months. Effectively turning a processing station into a prison for kids. That was not happening under Obama, Bush, anyone. This is new.
You better hope (for Trump's sake) that a kid doesn't die in these conditions. You thought the press was bad now? You ain't seen shit.