14. Equitable Estoppel. [See also Reliance]
 
    a. "Given the circumstances of this case, we reject the notion that the County's [mistaken] issuance of the business license and the health permit estops it from enforcing its zoning regulations against Mad Dogs [despite significant expenditures in reliance]. Where a public right and the protection of the public are involved, the doctrine of estoppel is to be invoked only in rare and unusual circumstances, and should not apply where it would defeat a policy adopted to protect the public." (citations omitted) In this case, it would be unfair and inequitable to apply estoppel to protect Mad Dogs, because to do so could harm nearby residents who were powerless to prevent the County's illegal issuance of the permits to Mad Dogs. On the other hand, Mad Dogs had the opportunity to inform itself of the County's zoning regulations and the need to obtain a conditional use permit."
Board of Co. Comm'rs v. C.A.G. Inc., 98 Nev. 497, 500, 654 P.2d 531 (1982). No. 27.
 
    b. Despite negligence in enforcing and interpreting zoning and building codes: "It would be an abuse of discretion in the instant case and contrary to principles of equitable estoppel to retroactively enforce reinterpreted zoning laws or to assert previously waived building code infractions after funds had been loaned and construction nearly completed. We hold that when a building permit has been issued, vested rights against changes in zoning laws exist after the permittee has incurred considerable expense in reliance thereupon."
City of Reno v. Nevada First Thrift, 100 Nev. 483, 487, 686 P.2d 231 (1984). No. 31.