It's not just Florida.
More than half of the states in the
United States have adopted the
Castle doctrine, stating that a person has no
duty to retreat when their home is attacked.
Some states go a step further, removing the duty of retreat from other locations. "Stand Your Ground", "Line In The Sand" or "No Duty To Retreat" laws thus state that a person has no duty or other requirement to abandon a place in which he has a right to be, or to give up ground to an assailant.
Under such laws, there is no duty to retreat from anywhere the defender may legally be...
http://en.wikipedia.org/wiki/Stand-your-ground_law