My guess would be that if you ladle a guy with a loaded sap-like object, you're going to have a bad day in court regardless if you were in the right.
If you beat him. up with that same thing and it's it's nothing more than a fist full of paracord, I think you'll be ok.
Personally, I would feel better armed taking some braided paracord and slinging my tangle of keys like a flail. I've got a couple for my truck, my wife's car, our old jeep, and about 8 metal keys for various doors in two office buildings.
Might be a foolish thing to do with your keys. However, if I'm going medieval with improvised hand to hand weapons, I'm probably out of ammo and broke my knife.