Fully solving tree Encroachment

This a WA state issue.

How does a tree encroachment issue get FULLY solved once and for all !

My neighbor has a 'non-fruit Thundercloud Plum tree" approx 30 feet high. The trunk is wholly on his property about 1 foot from the boundary line so a good sized portion of the canopy hangs over into my yard. The self help remedy has been used to trim back lower branches a lot but not all the way to the boundary line as I do not want to 'endanger the health' of the tree. i can't reach the higher branches. Needless to say, the tree branches just grow back over time and I'm tired of having to trim the foolish tree.
What gives him the right to have a tree which keeps growing into my yard??
Can he be compelled to remove this tree once and for all??????

Thanks.