You can't make up conditions after the booking, do you say that they can not have guests at the unit? Do you say that you need a photo ID of every person that enters the unit? How would you feel if you went to a store went to make a purchase with cash and then the clerk says I need a copy of your drivers license? You would be upset too. If there was a sign at the door of the store saying all cash purchases must be made with photo ID that would be understandable, but not after the fact.
It's a learning experience, add conditions to your listing so everyone is on the same page, shame on your guest if they don't read it, but shame on you for asking for something after the fact.