There is a lot of trespassing law that has already proven that you can't possibly follow a property line without occupying private space, either on the ground or in the air above it.
We aren't actually talking about the crime of criminal trespass (MCA 45-6-203), we are discussing Failure to Obtain Landowner's Permission for Hunting (MCA 87-6-415).
This is an important distinction in Montana, because just walking across unposted private land is not a violation of Criminal Trespass. Landowners have to either post property according to law, or give personal notice to any one person that they can't trespass, before such trespass becomes criminal.
Hunters have a higher burden than the general public though with the 87-6-415, in that there is no requirement for the landowner to post or notify the hunter.
That alone is an unfair application of law that discriminates against hunters, IMO.