since it appears that the hunting area and national park are adjacent. Unless there is a clear demarcation between the two areas, it's easy to see how you could end up a little ways into either side.

Regardless, it's the guides who should be liable because they are the ones leading the excursion and if there was an issue, they could have drawn a line in the sand and turned around. It's certainly possible that the hunter egged on the guides to proceed, but ultimately the person leading should take responsibility.