Here in the state of Texas, you have to have a Commercial Appliator's License, Catagory 3A or a Structural Pest Control License, if you receive any form of income/payment from any form of application of a pesticide. It doesn't matter if it is organic or synthetic. I have either built or maintained golf courses in seven states and noticed the application laws are remarkably similiar in scope and enforcement. With regards to fertilizer, I have never heard of specific application laws just for that.
The important point is wether or not you the applicator, receives payment.
I do work for the spokesman for the TDA, and he informed me license violation fees have gone up 3K% due to the budget shortfall. He also said contact with other States revealed fines are going way, way up as well.