Not everyone knows the legal ramifications surrounding removing a tree. Some communities have very strict laws pertaining to tree removal - some areas have no rules and regulations. You need to find out what your community expects when a tree is removed.
Tree ordinances can be enforced by both cities and counties. They may have no enforcements at all. If you live within the limits of any city you need to contact your city hall or city council member. If you live in an unincorporated portion of your county you will need to visit your county courthouse. You might also check to see if your city is certified under the Tree City USA program for extra information.
Arborist at Work, Anoldent/Flickr Photo