Florida

Dogs on leash may be used to trail wounded game mammals. You may track at night by flashlight, but it is preferred that tracking wounded game take place at dusk or the following morning if the weather permits. You are permitted to carry a weapon at night, but you are not allowed to discharge the firearm during non-shooting hours. Dogs can be used off leash to track or hunt deer in certain specially permitted areas. Check with the Florida Fish and Wildlife Conservation Commission for specifics.

State Regulations: http://myfwc.com/

United States:
Canada:

Green — Tracking allowed
Red — No Tracking allowed
Gray — Tracking allowed under certain circumstances or in certain areas of the state/province, but not all