US code is legislation/regulation. Case law of course would still exist even with minimal regulation, but absent byzantine network of legislation/regulation, it will be less complex, since less factors will be involved in the lawmaking. If you do not regulate how big soda cups must be to be able to be sold in a retail establishment, you do not need case law that defines what "sold in retail establishment" means, what "soda cup" means and is selling two small cups the same as selling a large one and what happens if two small cups look exactly like one big cup with a wedge in the middle. And so on. Congress creates over 50 federal crimes now each year, this makes the system more and more complicated every day, with bad consequences for everybody except lawyers that get to earn tons of money on navigating this insane labyrinth.