Earlier quoted context omitted.
People are pretty sensitive about government financial workers committing fraud, similar to how they are rather sensitive to government police committing murder.
Sadly, in neither case will you ever have 100% compliance. Pretending it's achievable, and trying to achieve it, is IMHO, silly. Remember the regulations do not prevent fraud, enforcement prevents fraud. There already exist plenty of things saying it's not okay, etc. Saying "and also, don't do that" is probably not actually necessary most of the time, in the same way saying "don't shoot people" is sufficient. Saying…
Anyone who's played rules-lawyering games like Nomic will be aware that banning all misbehavior explicitly is impossible. You're basically limited to whitelisting approved behaviors, or implementing a general rule against malfeasance. Unless the consequences of misbehavior are enormous, the second option tends to be more efficient.