Q. Attorney General Jeff Sessions got the whole country discussing the Bible when he quoted from Romans, “Let everyone be subject to the governing authorities, for there is no authority except that which God has established,” to defend the Trump administration’s policy (now discontinued) of separating the children of migrants from their parents. Was that a valid argument?

I’ll address the interpretation of that passage in Romans shortly. But let me make a preliminary observation first.
Sessions quoted the Scripture about obeying government authority not in support of a law, but in support of a punishment. Here’s what he said in his speech on June 14, 2018 to law enforcement officers in Fort Wayne, Indiana (text from the Justice Department website):
“Let me take an aside to discuss concerns raised by our church friends about separating families. Many of the criticisms raised in recent days are not fair or logical and some are contrary to law. First- illegal entry into the United States is a crime—as it should be. Persons who violate the law of our nation are subject to prosecution. I would cite you to the Apostle Paul and his clear and wise command in Romans 13, to obey the laws of the government because God has ordained them for the purpose of order.”
We can see that Sessions was trying to counter criticisms of the government “separating families” on the grounds that by doing this, it was prosecuting those who “violate the law.” As an aside of my own, I would observe that it’s an open question whether a person who enters a country without prior authorization specifically to request amnesty is breaking the law. But for the purposes of argument, let’s assume that it is. A government’s responsibility to enforce the law doesn’t give it the right to use any punishment it wants. The U.S. Constitution itself forbids “cruel and unusual punishments.” The question then becomes, what does the Bible say about the punishment that Sessions was defending for such cases?
One of the most poignant passages in the Bible is Jeremiah’s description of the people of Judah mourning over the children they were separated from when the Babylonians carried their younger generation off into exile:
“A voice is heard in Ramah,
mourning and great weeping,
Rachel weeping for her children
and refusing to be comforted,
because they are no more.”
The New Testament says that these words were “fulfilled” (that is, they took on a further meaning in light of later events) when Herod executed all the baby boys in Bethlehem in an attempt to kill Jesus. So in terms of family separation as a sanction, the Bible identifies Jesus with those who have suffered this punishment, not with those who would inflict it. It portrays the anguish that it causes, rather than celebrating those who use it to control populations. So I would say, to begin with, that it was not valid for Sessions to appeal to the Bible to support the punishment he was defending.
As for the passage in Romans itself, while Sessions stated that it taught that God has ordained the laws of government “for the purpose of order,” it actually says that “the one in authority is God’s servant for your good.” The Greek term is agathos; it’s also translated “welfare” or “benefit,” or “to help you.” In other words, the government is given power under God not to keep everyone in line with the way it wants things (to maintain “order”), but to promote the welfare of everyone under its control. Everything begins with God wanting good for people; God then creates governments as His agents to promote that good.
While not stated explicitly in Romans, the implication is that when governments fail in that responsibility, and particularly when they oppose what is good and become destructive of it, then God’s people no longer have an obligation to obey. Instead, they have a responsibility to disobey as a loyal protest, in order to call the government back to fulfilling its rightful role and original mandate.
(Incidentally, the American Declaration of Independence says essentially the same thing: “Whenever any Form of Government becomes destructive of these ends”—Life, Liberty, and the pursuit of Happiness—”it is the Right of the People to alter or to abolish it, and to institute new Government, laying its foundation on such principles and organizing its powers in such form, as to them shall seem most likely to effect their Safety and Happiness.” And so if Sessions was instead promoting an unconditional obedience to government, whatever its actions, he was undermining the original foundation of the American government itself.)
A single verse of Scripture never contains the whole counsel of God. We must consider the teaching of the entire Bible on a given question in order to understand the answer to that question in a full and balanced way. And the Scriptures provide numerous examples of people who resisted and disobeyed their governments in order to be faithful to God’s purposes. These examples are informative, and they fill out the picture provided in Romans.
Moses’ parents hid him rather than obey Pharaoh’s order to kill him by drowning him into the Nile. Shadrach, Meschach, and Abednego refused the command to bow down to Nebuchadnezzar’s idol, and they were thrown into a fiery furnace. Daniel broke the law that Darius passed that no one could pray to anyone but himself; Daniel continued to pray to God, and he was thrown into a den of lions. (In all of these cases, God miraculously or providentially preserved the lives of those who disobeyed for the sake of faith and conscience. We must recognize that this may not always be the case, and we must be prepared to suffer if necessary.)
Jesus himself was accused on many occasions of breaking the law, for example, when he healed on the Sabbath. His response was that it was lawful on the Sabbath to do “good.” In Mark and Luke, this is the exact Greek term that Paul uses in Romans (agathos); in Matthew, it’s a synonym (kalōs). Either way, the argument is the same: God’s desire to do good for people comes first; laws come second, to support that.
When the Jewish government authorities forbade the apostles from speaking about Jesus, they continued to do so anyway. When the authorities arrested them and demanded to know why they’d done this, the apostles responded, “We must obey God rather than any human authority.” So according to the Bible, obedience to government is not an absolute, unconditional obligation. Instead, God’s people have a responsibility to hold the government accountable for fulfilling the purpose for which it has been constituted, which is to promote the welfare of everyone under its control. By this test, the policy of family separation was not a biblically valid exercise of government authority.
We may note, finally, that the apostle Paul, who wrote in Scripture that everyone should be subject to the governing authorities, was himself executed by the Romans as a lawbreaker. The charge was that he was promoting loyalty to Jesus rather than to Caesar.