The discretionary immunity doctrine as applied to a public entity and an employee of a public entity pursuant to Sections 815.2 and 820.2 of the Government Code applies to decisions of a county department of agriculture and an employee of a county department of agriculture enforcing a state or local pest control or pest eradication statute, regulation, or ordinance. Nothing in this section authorizes or affects the filing of an action challenging the legal authority of the county department of agriculture to undertake the pest control or eradication action.