Is there a legal precedent that allows me to keep all the golf that land on my property?

I think if you find some in your yard, sure, but if someone is playing through and they hit it into your yard and want to get it back you should give it to them. I doubt any of them mean to hit it in your yard. I wouldn't let them play out of my yard though because of divots, but i'm sure you'de get to keep more than you tossed back.