In Canada here we have a strange definition of a weapon (as opposed to firearm or otherwise). A object becomes a weapon when it is used with the intent to harm/kill someone. Or something close to that, prevents shenanigans trying to skirt the formal definitions.

For this reason some bikers carry hammers on their bikes, y'know incase repairs need to be done. In the case of Nice, a truck is inherently a weapon. Can't really regulate every truck though