First, there are two laws in Montana regarding corner crossing. One is civil based on trespass being a strict liability tort and the other is MCA 45-6-203(1)(b).
Under the civil trespass any time any person enters your property without your permission even if they do not physically damage your property they may be liable for trespass. No matter how small a portion of your land they touch for even a brief moment…they may be liable for trespass. The strict liability damage for civil trespass is the presence on the property not any pecuniary loss.
Under MCA 45-6-203(1)(b), a person commits the offense of criminal trespass to property if the person knowingly…enters or remains unlawfully in or upon the premises of another.
Premises is defined as “real property” under MCA 45-2-101(60).
It is not just about “airspace” which you can trespass upon. An example would be Andy throwing a ball over and across Bob’s property to Chris. That is a trespass by Andy and Chris because the ball is passing through Bob’s airspace even though Bob is not suffering any pecuniary damage.
The issue that I see is that property lines are definite and infinitely thin in actuality, while GPS and fence lines are blurry. Which means that while you may not intend to step foot onto someone’s property you likely will when you cross a corner.
Simply knowingly “entering” someone’s property is enough under the statute. Thus, if you knowingly cross a corner and your gps takes you one, two, three, or more feet onto someone’s property then you may be civilly or criminally liable.
As a Montanan I’ll skip my rant about out of staters…
Corner crossing is not as gray as some think. As of right now anyone that enters someone else’s property no matter how ephemeral their time is, they may be criminally charged or civilly liable. Also, trespass allows for attorney fees. So, if you are civilly liable you’ll have to cough up for the land owners lawyer too.
That is just my interpretation.
I support corner crossing. I also support the right to exclude people from your private property.
Good Luck