The Atlanta Tree Protection Ordinance specifies in Section 158-33 that:

The bureau of parks and the bureau of buildings shall be charged with the enforcement of this article. The city forester and the city arborist have police power to do all acts necessary to ensure that the provisions of this article are not violated, including, but not limited to, the issuance of citations for the violation of any provision of this article. In instances in which an individual or firm is found cutting or otherwise destroying a tree without a permit to do so in their possession, the Atlanta Police Department shall require such person or persons to cease such operations until a permit is obtained.

Please print this article and show it to the police officer if you need to call one to stop illegal tree cutting.  Not all police officers know that one needs a permit to damage or cut trees, even when the tree is dead, dying, diseased or hazardous.