Well don't show or tell them where it is! Also if they are friends, family, etc they should not want to hone in on your spot unless you invite them. I know it isn't easy I have had to deal with this myself, but you have to lay down the rules and if they don't care to abid by them then a tough desicion maybe in the waiting.

In my area it is illegal to hunt in someone stand, without written premission...but I would hate to have to resort to that!

Tough one, but I would just try and be honest with them. Hopefully they will respect your wishes and not have an all out brawl.