"v" wrote
When you say it "moves freely" - what do you really mean, that you can
rock it back and forth, spin it around a few degrees? Why do you have
to remove the stump anyway? How is the neighbor the boss of you?

Thanks all for the intelligent, proven ideas. The neighbor complains that
the roots are damaging their plumbing and that the branches scraping their
bedroom roof are just too dangerous. I just got a call from the city saying
that they'll take the stump for free if it's pushed to the curbside. I will
inspect for the fibrous root underneath again, which we suspect are gone
since we rock the stump from side to side (2'). But first we'll move the
stump upward a inches or so to get a good view down there. I apologize
for the size, as a few posters notice. It's actually nearly 3 ft cubed (27 cu ft)
but not 3 cu ft. Thankfully, another poster (Mark) posted photographs
identical to my problem. The same driveway, location, fences,
dirt, and tools. The only difference is that the stump and dug hole are
almost about "two or three times" as great compared to these pictures.
http://www.bunchobikes.com/tree.htm

I assume a neighbor may complain if the tree is within a certain
distance from their property. Or if the roots of a line tree or
neighboring tree cause problems, an owner can abate the nuisance.
Civil Code Section 3502. Can anyone advise if I'm interpreting the
law correctly? Thanks.