Laws, Regulations, and Licensing Requirements
The regulatory stack
Fumigation is governed by overlapping federal and state law. FIFRA makes the label the controlling document: a use that differs from the label in site, rate, method, timing, or PPE is a violation regardless of whether it works. Nearly all structural fumigants are Restricted Use Pesticides, so they may be applied only by, or under the direct supervision of, a certified applicator.
States add a second layer. In California, the Department of Pesticide Regulation sets the rules and county agricultural commissioners enforce them; branch licenses (structural fumigation), company registrations, and dealer/advisor certificates are all separate credentials. Understand who may supervise, who must be physically on site for gas introduction, monitoring, and clearance, and what tasks an unlicensed helper may legally perform.
Routes for non-label uses
Know the difference between a Section 24(c) special local need registration (state-specific, must be in hand), a Section 18 emergency exemption (crisis only, expires), and a Section 2(ee) recommendation, which covers limited deviations for an existing labeled use - not a license to improvise structural fumigation.
Traps
Assuming a state rule can relax a federal label (it cannot); treating "supervision" as a phone call when the rule requires on-site presence; confusing posting requirements with recordkeeping retention; forgetting that the certified applicator's name on a report does not transfer liability to a helper who acted outside supervision.
Rule of thumb: when label and regulation both speak, comply with the more restrictive requirement - never the more convenient one.
Worked example: a label allows 16–32 oz per 1,000 ft³, but the state maximum is 24 oz. The legal use window is 16–24 oz, and the record must show a number inside it.