IF the property was located in Sonoma County, CA -
illegal means exactly that .............
The Sonoma County Code imposes mandatory civil penalties for building, zoning, non-storm water discharges and certain health code violations. These penalties may be calculated in one of two different ways. When a permit can be issued to
legalize a violation, penalties may be imposed from three to ten times the base permit fee.
If the violation cannot be approved or legalized by a permit, you will be given (30) days to cease the unlawful use or demolish the unlawful structure.
What will happen if I don't get a permit and resolve the violation?
Code Enforcement staff strives to assist the property owner to obtain compliance. If permits are not obtained, a "Notice of Abatement Proceedings" will be
recorded against the title of the property. This recorded document serves to notify the public of the violation and
may prevent you from selling the property or obtaining refinancing or title insurance on the property.
In addition, an administrative abatement hearing may be scheduled in an attempt to gain compliance. If the Hearing Officer orders that you correct the violation and you do not comply, your case may then be referred to County Counsel to be pursued in Superior Court.
This could result in a judgment against you, increased costs and penalties, the County entering your property to physically remove the violation, and in some extreme cases, owners may be sentenced to jail time.
http://www.sonoma-county.org/prmd/FAQ/code-enf.htm
The above process is NOT unique. It behooves each Appraiser to perform requisite due diligence NOT ONLY ON ZONING issues but also Building & other governing Municipal Ordinances.
Should a specific Municipality NOT have similar Local, County and/or State Laws governing BOTH Zoning and Building Legal Uses ............simply report the due diligence performed and the impact, if any, the lack of governing ordinances has on market appeal and market value of a subject's property.