What do you mean when you say God’s law is case law?

God’s law is not statute law. It does not spell out every possible infraction but rather gives a single case from which we are expected to grasp the principle it embodies. Which principle we are then to apply wherever it fits.

A case in point is the commandment to build a fence around one’s roof. At that time roofs were flat and were used as living space. To fail to have a fence around it would permit a hazard to exist. Today, where we have roofs that are not used as living space, we do not fence them in. This is not a violation of God’s law because the law is not embodied in the letter of the case but in its principle.

God’s law, as case law, tells us at this point that we must fence swimming pools, excavations or other conditions that could represent hazards. All of God’s laws, including His civil laws, those requiring action on the part of civil government, must be obeyed in this principled sense.