Under Civ. Code 3482, an act done under the express authority of a statute, regulation, permit, license, or other governmental approval cannot be a nuisance.  The defendant water districts successfully invoked that defense to a complaint charging them with a nuisance for adding chloramine to drinking water in an effort to kill germs.  The chloramine allegedly caused pinhole leaks in copper piping.  But the water districts had added the chloramine under a Department of Health Services permit.

California Court of Appeal, Fourth District, Division 3 (Ikola, J.); May 3, 2018 (modified May 18, 2018); 2018 Cal. App. LEXIS 401