You need to respect certain minimum distances which may be governed by local regulations so the first step is to ask at your mairie if there appropriate bylaws.
If there are no specific rules, then the regulations of the Code Civil apply.
This is with the proviso that there are no minimum distances in Paris and urban areas in its suburbs (however, even there, trees should not cause obvious nuisance to a neighbour due to growing too high and there could be financial penalties if this happens).
Otherwise, distances are measured from the middle of the trunk to the wall and are two metres minimum for trees that are more than two metres high and 50cm for shorter trees.
However, if the wall is shared, then the measurement is up to a point in the middle of the wall.
If you own the wall then the distance includes the full width of the wall; if it is your neighbour’s wall, it is measured up to the face of the wall bordering your property.
If the rules are not respected, your neighbour can go to court to demand that the trees are removed, moved or reduced in height.
Question answered by Sarah Bright-Thomas of Bright Avocats