Each state enforces their laws differently, but all use federal guidelines (EPA) as a basis. There are "restricted use" chemicals, and then "non-restricted use". The non-restricted use products are available to virtually anyone, in any volume, at any strength. Restricted use products are available to licensed "applicators" only, through vendors that also must meet certain criteria. There is no such animal as a lesser grade/lower concentration/smaller container availability of these products. They are usually sold through AG supply houses, landscape supply dealers, or commercial chemical dealers. You must be certified in a particular avenue of use. (i.e. residential lawn application, Golf course application, AG use, ect) You must have certification to PURCHASE restricted use products, even for use on your own land.

You CANNOT spray, even non-restricted use products on someone elses land OR do it "for hire" without proper certification. The testing and certification is usually done through state agricultural agencies (at least in my home state it is. I understand that's the proceedure in most others as well) Most states also restrict commercial application of liquid (and in some cases granular) fertilizers

Bottom line is, you CAN use non-restricted use products on your own land, BUT law requires you use it in a SAFE, RESPONSIBLE manner, and ACCORDING TO MANUFACTURERS RECOMMENDATIONS FOUND ON PACKAGE LABELS.

Certification requires proper knowledge of sprayers, under what (weather) conditions you can or cannot spray, saftey issues, proper documentation of use, and certificate of insurance for pesticide use. (Pesticide is a generic term for anything that "kills" "nuisance" plants or creatures.)

With the advent of "lawn care operators" in recent years, the EPA and state agencies are now tasked with regulating use of pesticides. They are gunning for those who mis-use such. Also, the licensed applicators are out to "discourage" the use of pesticides by anyone who hasn't dotted their I's and crossed their tee's. In other words, there are people with an economic stake in this subject that would gladly turn you in for improper use of pesticides. Fines are steep.