early cancelation

[Katherine8]

A guest booked a 22 day stay and now wants to leave 13 days early.  

What is the Airbnb policy on this?  Is he obligated for the balance? 

I really don't want him cancelling his reservation and "freeing up" the unit until I am sure he has left it in good condition.  So I do not want to allow him to cancel his stay until he is out for my liability and security. 

 What if I can't re-rent it ?

Thank you

Katherine