Xp_instance_regread

Determining Public Access To Xp_regread And Xp_instance_regread

I am trying to write a query to determine if public role has access to both of these. I need this to satisfy auditing requirements. If anybody knows how to write the t-sql to turn these on, I should be able to use the sql to find out if public role has access to these. Or if you just have a script already or a sp that would be fantastic also.
Thanks
Kyle