Here in Finland we have “every man’s rights” that allow people to pass through anyone’s land and even collect berries and mushrooms. However only non motorized traffic is okay and no fire making, no wood cutting, no collecting of moss etc. Main rule of the thumb is “stay out of sight of any residence”. Basically it does not apply to van life at all, since you would need landowner’s permission to drive off the road in the first place.
Limits to above are certain obvious places, like army training grounds, border zone… umm… nuclear plant had a no go zone around it. But in general, pretty much anywhere is okay to go on foot, bicycle or horse.