As a security officer in a Las Vegas casino we have been notified that O.C. (pepper spray) training will no longer be voluntary but mandatory (ie: you can loose you job if you don't complete the course). Many officers have been here a long time and don't want to participate in this training, some of these officers have medical conditions. (Would you want to spray a decorated POW WW II veteran?). We are security officers NOT law enforcement officers.
Question: Do they have the right to fire anybody who cannot or will not go to this training session, because the company has changed their policy??
All advise legal or not is greatly appreciated.

Yes, they do. If you do not want to use the tools that the company provides, then that isn't the job for you anyway.