The law that is invoked in these cases is extremely vague and broad. Basically the law says you cannot commit fraud when trading securities. The whole thing is about 50 words. Nevertheless, over the years the courts have built out a huge body of case law that details what counts as fraud, and among this case law is a lot of rules on edge cases around insider trading. Based on these rules, companies have developed things like blackout periods where employees are not allowed to sell stocks, and 10b5-1 stock sale plans in order to avoid insider trading.

So sure, these rules are not technically "law" because they were developed by judges and not Congress. But if you break those laws you'll be convicted and maybe go to jail all the same.

At the same time, I don't think that just because it is "judge made law" means that it's necessarily bad. In the case of insider trading, Congress basically punted on the issue and forced the courts to specify what does and does not constitute insider trading. It would probably be better for Congress to clearly define the rules, but they didn't so the courts had to do it instead.

In the US, our system of law is based on our Constitution, in this case the Fourth Amendment to the Bill of Rights. Like several other amendments, this one is written vaguely enough to allow outrageous interpretations by biased or incompetent judges. This is one of those situations.

If you can look into Fourth Amendment law without growing steadily sick to your stomach, you're either on the government's side or you have a stronger stomach than mine.

Yes, and when those precedents are binding, they are called "case law" aka judge-made law. It's not a perjorative, most of the time. It's simply how the law works in countries like the US.

https://en.wikipedia.org/wiki/Judge-made_law (redirects to "Precedent")