groundpounder

In the city and county of Denver the "street trees" are owned by the city, but the responsibility for their care lies with the homeowner if it is in front of their home. You must have a permit to do anything to one of these trees. There are code inspectors that cruise around and hand out citations for pruning, removal,etc. American elms must be protected from DED. The cost of all of this is on the home owner, although the city will take care of the problem if the homeowner can not afford to and will set up a pament plan.
Several years ago it became popular to buy an old home in the city and scrape everything off of the property and rebuild. As Treestyle said, the benefit of these mature trees that were being scraped off did not end at their respective property lines. The city could do nothing about the problem as it was private property. Long story short,neighbors and Arborists got together to educate the new property owners as to the value of what they had and how to protect them during the scrape off process, and trees were saved. Of course there were the Aholes that removed trees any way because they owned them and nobody was going to tell them what to do (picture your three year old screaming "MINE, MINE, MINE!) but the public was educated and the tree guys gained some lifetime customers. Scrape offs are no longer as popular as they were, but the effects of the grass roots effort remain even today.