If you zoom in on the area on Google maps or arcgis it has the boundary line. I personally find it interesting. From Bowen Ranch parking to the springs you pass through two fences. If you hike in the Pacific NW we don't even have a fence with Canada! Literally there is just a marker in the ground saying Canada is here and the US is here, one foot apart.
The 15 day restriction is likely to deter people from establishing hippie communes or similar.
Reiterate the appreciation in your work to dive down there and keep the bottom clean. On my last visit there was a person who passed me carrying a full camping load and a large bag of trash in a see thru bag, so there are good folks.