This is precisely the logic behind qualified immunity: "you can only jail them if they knew it was illegal, otherwise they get a slap on the wrist and politely asked to stop". It sounds nice in theory, but the inevitable result in practice has been total immunity for all lawbreaking, because of a compliant court system which sets the bar for "should have known it was illegal" to be impossibly high. Maybe at one point before we knew this it was possible to argue for QI in good faith, but now we empirically know it's an unworkable standard and should be scrapped.

Besides, civilians get the "ignorantia juris non excusat" [0] principle, and the rule of law means that everybody, including government officials and law enforcement, should be held to the same standard.

[0]: https://en.wikipedia.org/wiki/Ignorantia_juris_non_excusat