Neighbors tree trimmers trespassed(?) onto our tree main trunk from their side of the fence

Location: Los Angeles County: The tree trimmers our neighbors hired to cut the overhanging branches into their side of the fence were using the main trunk in our yard to cut the branches. They were climbing in the tree on our property which the accessed from their side of the fence and did not have permission from us to access the branches in this way.

We told them to remove themselves from our tree and not trespass again which the immediately did. I think this would be considered trespassing but not sure what constitutes that.

Appreciate any insight or thoughts about this.