In T.C.A. § 5-1-118(c)(3), the law provides further that all court decisions and statutory laws relating to variances and nonconforming uses applicable to zoning ordinances and land use controls shall apply to the enforcement and exercise of these new regulatory powers.  For example, if a county determined that the sound of planes taking off and landing at an airport could potentially be a nuisance to surrounding residential properties and passed a regulation prohibiting the location of an airport within one-half mile of a residential property, this regulation may limit the location of future airports in the county, but an airport that was in existence at the time the regulation was passed that violated the distance rule would be allowed to continue to operate as a pre-existing nonconforming use.