Short answer. For overhanging branches, you may only demand that your neighbor cut them — you cannot cut them yourself. For roots that have already penetrated into your land, however, you may cut them yourself within your own property. Article 680 of the Civil Code draws that clear line.
What the law says
the owner of the latter shall have the right to demand that they be cut off insofar as they may spread over his property, and, if it be the roots of a neighboring tree which should penetrate into the land of another, the latter may cut them off himself within his property.
Civil Code, Article 680 — Overhanging Branches And Roots. Read the full provision →
Two different rules for branches and roots
Article 680 of the Civil Code distinguishes sharply between overhanging branches and encroaching roots. For overhanging branches: you have the right to demand that they be cut back to the boundary, but the right to act is the neighbor's — you cannot simply take a saw to their tree. For roots that have penetrated into your land: you may cut them off yourself, but only within your own property. The self-help remedy applies only to roots, not to branches.
Why branches are treated differently
Branches belong to the tree, and the tree belongs to the neighbor. Cutting them is the neighbor's responsibility because they own what is being cut. The law gives you a right to insist — you can demand that the pruning be done — but you do not acquire the right to enter the neighbor's property or to act as if the branches were yours. A tree's canopy extending over a boundary is a nuisance the neighbor must remedy; it is not an invitation for you to take over.
Roots: self-help is allowed within your land
Roots are different. Once they have physically penetrated your land, you may cut them within your own property without needing the neighbor's permission or a court order. The limitation is territorial: you may only cut what is on your side of the boundary. You cannot go onto the neighbor's property to address the root at its source. But within your own estate, the self-help remedy is clear and does not require any prior demand.
If the neighbor ignores your demand about branches
If you have demanded that the neighbor cut the overhanging branches and they have refused or failed to act, your remedy is not to cut the branches yourself — it is to pursue legal action. You may seek a court order compelling the neighbor to perform the pruning. Document the overhang and your demand. If the branches are causing actual damage — falling on your property, blocking light essential for a specific purpose — those damages may also be recoverable. Get legal advice if the neighbour remains unresponsive, especially when the overhang is significant.