You need to check your states statutes. In Florida as I expect in most states that it says:
REGULATION OF PROFESSIONS AND OCCUPATIONS Chapter 487
PESTICIDES View Entire Chapter
487.031 Prohibited acts.--It is unlawful:
(1) For any person to engage in the application of restricted-use pesticides, except as defined in chapters 388 and 482, without a certified applicator's license issued by the department unless such person is doing so under the direct supervision of a licensee.
LINK:
http://www.flsenate.gov/Statutes/in.../SEC031.HTM&Title=->2003->Ch0487->Section 031
Pesticide Certification Section
Pesticide Applicator License
Restricted use pesticide applicator licenses are available to certified individuals to allow for the purchase and use of restricted use pesticides on agricultural and related sites, such as farms, plant nurseries, forests, ornamentals and turfs not associated with structures (such as golf courses and parks), and highway right-of-ways, etc
LINK:
http://www.doacs.state.fl.us/onestop/aes/pestapp.html
To use exempted products no license is required.