Applying strong herbicide on unadopted land

My small back yard and all the beds I have put in is losing a battle with field horsetail. I want to try and chemically kill the plant before starting again next year with my planting. What I’ve noticed is the back alley behind my house is also filled with of them. What are the rules about applying something like Kurtail on this land too. If I want to give myself the best chance of them not spreading in the future I feel I have to attempt to go at those off my land aswell- but am I risking getting in some form of trouble. Or am I just overthinking?

Any thoughts?