Under the City of Kellogg, Minnesota’s zoning code, solar energy systems (SES) and solar and earth­sheltered structures are permitted uses, provided certain requirements are met, that may be exempt from certain restrictions by variance. The provisions also forbid vegetation or structures in residential districts if they cast a shadow on an existing SES greater than a determined standard. That standard does not apply to vegetation and structures existing at the time of SES installation. Violation constitutes a private nuisance that gives rise to a legal cause of action for the impaired owner or occupant. City of Kellogg, MN, Code § 220-56.