I would recommend maybe this slight change: (or something similar)
No Firearms Allowed
Except lawful concealed carry according to
Oklahoma TITLE 21 § 1290.1 and TITLE 21 § 1290.2 Paragraph 1
I like that a lot. I'm going to run that by them.
The best part of this is that because THEY brought it up, I'll also be able to carry in my office... legally.