But you can be surprised when the police don't let you go after realising the thing is mostly blunt. What looks like a knife edge on the right hand side of that picture isn't sharpened like a knife, it's more like how a spade has a keened edge, because it's a fancy type of trowel. The saw edge is sharp though, but again, not as sharp as a wood saw.
Plus, the law allows for the carrying of a knife for a reasonable legitimate purpose. The accused was carrying a basket of vegetables, having just harvested them using the "knife". It's a legitimate purpose, and it wasn't even a knife.
Add on that it was also sheathed, and we have a clear case of moron cops being heavy handed and abusing the law.