Is that true though? If something is technically legal like this, they get found innocent. When its technically illegal, mandatory minimums insure they go to jail for far too long. Someone once said there are legal traditions where intent of the law could be used to find guilt, and it had a name, but the US and UK are much more like machines.
I believe both the US and UK (as do most western countries?) have 'common law' systems, where jurisprudence / case precedents are heavily relied upon. Whenever there is doubt on the legality of something, that court decision will set the tone for others to follow, and go higher up the justice system as needed.
The main point was that you can't simply blame the law for failing to 'replace judgement'. Most laws rely on some amount of common sense to be interpreted.
