This never really made sense to me as a kid:
"You can't do that! That's forbidden!"
- "It is is not forbidden as long as you are not caught."
To this day I don't quite follow that logic, over-thinking whether it is a similar existential dilemma as "If the pope shits in the woods but no one is there watching, did it ever happen?", but since it was kids who used to say it, I presume it had a simpler meaning more like "I don't care if it is forbidden.".
Well then, why not just say so? That is like saying:
"The sky is blue!"
- "No it isn't, as long as I am not staring at it!"
Yeah, whatever, kids are so damn stupid...