But policy is whatever the executive wants to do (within the law). It changes as administrations change. And asking the executive to change its policy is begging the Big Man to do you a Grace-and-Favor. Law is written by the legislature, and when it is promulgated, it binds the Big Man and all the minions of government as much as the poor schmuck at the border.
So, why are children being separated from parents at the border? Well, imagine that I am taking my family on a big trip to Turkey. I land at Ataturk Airport in Istanbul. And there, it is discovered that my papers are not in order. I am in the country, but I haven't officially "entered" it yet -- and I may have to get back on a plane at leave it forthwith, unless the problem can be resolved. The US consulate is called, the airline tries to clarify ticketing, our passports are being examined. Meanwhile, we wait in a sterile little room at airport Security. If we have to stay overnight, they may be nice and arrange a stay at a nearby hotel, but you can be sure there will be a policeman right outside. Inconvenient as all this is, my children are not separated from me. We are all in the same situation, trying to get our right of entry recognized and continue with our vacation. The same situation obtains in America if a family from somewhere else doesn't have their papers in order when they arrive here.
Now, imagine that I am apprehended while attempting to cross the Turkish border at night from Greece, or maybe Syria. In this case, I am not a confused tourist -- an uninvited guest. I am a (potential) criminal. I am going to jail, at least for the night. And whatever the Turkish law enforcement system does with foreigners arrested and charged with crimes is what is in store for me. As for my children, I don't know what the Turks do in that case. I do know what happens in America, when parents are arrested and minor children have to be cared for. Minor children are not put in jail with adults, even with their parents. Nor are they put in the juvenile justice system. Usually, they are put in Foster Care, at least temporarily.
We do this because we think it is better for the children than to be confined in an adult detention center, even with their parents. And we look for people to care for them while the adults' case is determined, and perhaps even bail granted. Which means we look for relatives first. In the case of ICE, that means they are putting illegal immigrant children in the care of relatives already in America, who often connive at their disappearance. This drives the ICE nuts, but they are bound by the law.
So, the first question we have to ask is, are illegal immigrants (with children or not) confused tourists or lawbreakers? If lawbreakers, do we grant them bail, given their risk of non-appearance? (We used to do that routinely, and bail was as routinely abused.) If we refuse them bail while their cases are being adjudicated, what do we do with their children? The law says they are not responsible for breaking the law with their parents, and shouldn't be put in adult jail. So, what do we do with them?
This leads to the next question, which is, could we not create some sort of not-quite-jail for families whose cases of illegal entry are in process of being heard? Yes, we could. But to create this by policy is a dead-bang loser, since no matter how nice such a detention center would be, the demagogues will immediately label it a "concentration camp." Who wants that headache? No, if we are going to do this, this category of detention center needs to be created by law, not policy. That means Congress needs to pass a law (and appropriate money to carry out the law).
Congress, of course, wants to do no such thing. Congress has steadfastly refused to do anything serious about immigration for years, because all their different constituencies will punish them for whatever they do, or the voters will. But only Congress can do this.
Jeff Sessions is doing all of us a favor. Yes, Sessions is a hard@ss, and I have my disagreements with him (on Civil Asset Forfeiture, just to name one). But he's the best kind of hard@ss, the kind who will enforce the law, WHATEVER the law is. Which means that if his enforcing the law as written causes Congress to get off its duff and write a better law, then he will enforce that law, and we'll all be better pleased.
But really, don't complain to the Executive and ask for policy to change. Complain to Congress, and make your views known. Only when Congress quits ducking its responsibility will this mess get better. Restoring respect for the Rule of Law starts with appealing to those who write the law, not those who have to enforce it.