Fighting Nature

There is a path behind our veggie garden that needed weeding, so I decided today was the day, and while I was weeding, I did realize that I can never win against nature, just hold it off.

This is before I started. You can see that grass is coming from the neighbor's yard, without permission. (Just kidding Carol).  The question is, short of building a wall, how can I stop it? 

For now, I have won out over nature; not sure how long this will last.