Odd question, but does anyone know for sure?
Seems like this would be illegal.

Just to clarify... in the US.

I would tend to agree with you, but I am not sure that all states recognize disabilities for which one has a service dog. The one example I can think of is that apparently in California a person subject to depression may have a dog as a companion and it is recognized as a service dog. Would that apply in other states?

Since you are voluntarily staying at a hotel, I think the hotel would be able to charge you a service fee.

Google is amazing

straight from the Dept of Justice website http://www.usdoj.gov/crt/ada/qasrvc.htm

"Q: Can I charge a maintenance or cleaning fee for customers who bring service animals into my business?


A: No. Neither a deposit nor a surcharge may be imposed on an individual with a disability as a condition to allowing a service animal to accompany the individual with a disability, even if deposits are routinely required for pets. However, a public accommodation may charge its customers with disabilities if a service animal causes damage so long as it is the regular practice of the entity to charge non-disabled customers for the same types of damages. For example, a hotel can charge a guest with a disability for the cost of repairing or cleaning furniture damaged by a service animal if it is the hotel's policy to charge when non-disabled guests cause such damage."

It seems you would be correct, it is illegal

http://www.usdoj.gov/crt/ada/animal.htm

Q: Can I charge a maintenance or cleaning fee for customers who bring service animals into my business?

A: No. Neither a deposit nor a surcharge may be imposed on an individual with a disability as a condition to allowing a service animal to accompany the individual with a disability, even if deposits are routinely required for pets. However, a public accommodation may charge its customers with disabilities if a service animal causes damage so long as it is the regular practice of the entity to charge non-disabled customers for the same types of damages. For example, a hotel can charge a guest with a disability for the cost of repairing or cleaning furniture damaged by a service animal if it is the hotel's policy to charge when non-disabled guests cause such damage.

TxTravelPro:
Found this website for you.
http://www.usdoj.gov/crt/ada/animal.htm

sorry guys did not realize others had already answered

I swear I tried to google it before posting... I must have used bad keywords. Thanks so much for helping me out. I have a hotel I am working with that documents that they charge and I really felt something was kooky with that...
I started my conference call with them 14 minutes ago, so these responses will make me look like I am really well informed!
Thanks!!!

Tx, I put in "Hotels fee service animal" and got the same site.

LOL it looks like we all found it at the same time!