In California (other states vary to varying degrees) there is a crosswalk at every intersection whether marked or not (as well as some marked crosswalks in other places). These are the only places a pedestrian may legally cross a road. Here cars must yield “right-of-way” to pedestrians, but pedestrians also have a “duty of care” for their own safety and others. Cars must yield but pedestrians can’t just step right out and damn the physics. On the road, pedestrians are confined to walking against traffic on the left side of the road if there is no sidewalk. Otherwise they should not be on the road. But, if they are on the road, drivers have a duty of care for their safety. Pedestrians can’t be there but if they are cars can’t just mow them down.
In practice, pedestrians generally don’t get tagged for jaywalking. (Walking in my neighborhood without jaywalking would be a death sentence because of blind corners. You have to cross the road often to be seen.) Where the law mostly comes into play is when pedestrians are struck by vehicles. A jaywalking pedestrian will likely be found legally responsible for the accident unless the driver was speeding or otherwise acted irresponsibly, in which case a percentage of responsibility will be assigned to each.
The point is, there isn’t a law otherwise. It isn’t illegal. Can you point at the law that says you may wear a sweater in the US? No, there’s just no law otherwise. It’s the default state.
> These are the only places a pedestrian may legally cross a road.
That’s crazy. Why restrict pedestrians like that?
> I once came upon two guys duking it out in the street. I can’t believe their only crime would be fighting in the UK.
Well I think you can be obstructing the highway, but crossing normally isn’t doing that.
Physics.