If the tree branches blocked a stop sign or its roots were pulling up a sidewalk then it was an encroachment onto public property.
The city certainly could request he do something about that.
BUT if his remedy is to remove his tree then that should be his right to take the tree out altogether. If the city wants shade then it need to plant its own tree.
city's Department of Health and Human Services sent him a letter, which he interpreted to mean that he should trim the tree. "And it says that, 'I am responsible that I should not allow or maintain any growth of shrubs, bushes or trees to extend onto or over any portion of the public way, including sidewalks,'" he said.
The letter definetly says bushes or TREES.