And the exact application of those few laws in nearly infinite situations would require first a caste of extremely powerful judges, and later an accumulation of precedents which would effectively become a massive and complex legal code in itself.
Of course, juries work better when they are able to find on both the facts and the justice of the law. We've deviated from this at our peril.
Mens rea, criminal intent, has historically been the simplifying agent in law. That's why you don't see a terribly complicated set of case laws surrounding, say, murder. The problem with lots of current criminal statutes is that you can be guilty of violating them without any intent to harm.
Common law has tended to focus obsessively on mens rea. Statute law has tended to disregard it. The difference probably has something to do with having to make a judgement about a particular case with the humans that are going to be affected standing there in front of you, as compared to dreaming up a bunch of laws in the abstract, or coming up with laws to address a politically attractive but wildly uncommon situation.
I believe this argument is empirically strong. You can see for yourself that there are (at least) hundreds of years of case law about murder. And yet the law surrounding murder seems quite a bit more straightforward than the laws surrounding, say, exporting electronics. This is because criminal case law has been sharpened by a focus on criminal intent.
http://www.huntingtonnews.net/state/090605-rutherford-statet...
And in any case, arguing around the edges of self-defense is a far cry from the sort of felony paperwork violations that got us into this discussion.
So perhaps the most clarifying question I could ask is: how many examples can you find of case law criminalizing paperwork mistakes with no criminal intent or intent to harm others, as compared to how many examples of that are there in statute law?
Like (I think) most reasonable people, I'm not in favor of criminalizing paperwork mistakes with no criminal intent.
What about if, in self-defense, someone goes further than necessary? He's attacked and choked by someone bigger and stronger. He reasonably fears for his life. Through chance or skill, he gets the upper hand, and knocks his attacker out. Then, before caveman adrenaline has faded, he slams the guy's head into the pavement until he dies. Do you apply the single "thou shalt not kill" law?
I don't really want answers to these specific questions, but to the meta-question: how do you handle actions which are harmful to society, but which cannot be resolved by straightforward common-sense ethical reasoning?
The hard, borderline cases that you mention are relatively rare. No matter how complicated your system of laws, these cases tend to require humans, either judges or juries, to make a careful decision.
If you have 10,000 laws rather than 10, you end up instead having to decide which of the many conflicting laws that could be applied should be applied to the situation. In marginal cases, human judgement is extremely difficult to replace.
One simple law about theft that can't neatly answer the question seems preferable to the current tens or hundreds of possibly applicable pedantically worded laws that can't neatly answer the question.
Common law? Worked out pretty well for the English for about 1000 years.