Your GS is probably too smart for this, but when DD refused to potty train, I waited until she turned three then told her a big fat lie. I told her that 'the law' was that when you turn three you have to start using the toilet. I said it with such a straight face, and kept up the pretence with a trip to the shops to buy the insert seat, that she totally believed me and toilet trained in one afternoon. There were a few tears, but I just said 'I'm sorry honey, it's not up to me. It's the law. When you turn three you can't wear nappies anymore' and DH nodded empathetically. Not sure if it was great parenting or terrible parenting, but it worked!
Personally, I think this approach is abusive. Little children take things quite literally, and adults can traumatize them with ideas like this. I'm sure you meant well and thought you were doing a good thing, but try to see what you said from the perspective of a tiny little kid who might have been thinking she'd go to jail for wetting her pants.
