@Michael1107
If it is before accepting the booking request, remind the guest clearly that the listing states your check in time from X to Y. If that does not suit them, they should withdraw the request asap.
If they only tell you after they book, but according to the cancellation policy, they are still entitled to a full refund, tell them either they can either check in between the times specified on the listing, or they should cancel.
Unfortunately, you have to sometimes get a bit strict about this, or guests will walk all over you. It has also been my experience that if you allow gussets to do this, they may well continue to ignore every other house rule or whatever is stated on your listing. We have a saying here: "Give them an inch, and they will take a mile." So, stand firm.
If the period for a free cancellation is over, then it gets a bit complicated, and you may need to involve Airbnb CS (which is not ideal). However, if you use IB, and it's an instant booking, you do have the option to cancel three bookings penalty free, 3 x times in one year, if you believe the guest will break your house rules. Not complying to clearly stated check in times is, to my mind anyway, a breach of house rules.
Hope that all makes sense!
Here is a discussion I started a while back on this topic, as I also found this problematic, although that was more to do with guests wanting to check in early...
https://community.withairbnb.com/t5/Hosting/How-can-I-stop-guests-ignoring-the-check-in-time/m-p/304...