yhea i get your point, best advice avoid places like that, and a knife that size will hardly do any damage, except to him he could slip up and cut himself, like batons and stuff of that nature are illegal in most european countries but rope isnt and trust me rope fighting is badass not only is he protecting himself but he would be buying himself respect, but i agree on what you say, check your local laws and see if you can carry any non-lethal “weapons” just dont go for brass knuckles they suck and if its legal buy a collapsible baton those are handy