Interesting question. I remember the recent thread about how much sgian dubh to show and have answered the question for myself recently. I was to a fund raiser which was held in a bar early in the night. When the fund raiser was over the bar continued a normal night, so ...
When I arrived My sgian was well visible.
As the fund raiser ended and I found myself in a bar, my sgian got pushed far down into my hose.
As I stayed longer still and the bar filled I removed the sgian from my hose and hid it under my arm.
Technically it wasn't illegal until I hid it, but it was surely against the rules of the bar from the start. They also let me enter without ID and I wonder how much the kilt had to do with that.