Home inspection requires exhaust to attic exterior
You'll want to check with your local government.  The sale of a house often requires some things to be brought up to current code.  What things are required, depends on the local government. 

For example.  In my area, sump pumps are required. If you're selling a house without a sump, you'll have to install one before you can close. A nearby area requires hardwired smoke detectors be installed before closing. 

Selling a house where an inspection is required, means you'll have to pass the inspection before the sale. 

If this inspection was done by the buyers (buyers inspector), they have every right to request whatever repairs they want. You as the seller have every right to deny the request, renegotiate,  or cancel the deal (assuming you haven't finalized the contract). You might want to contact your lawyer.