Self Insured's vs. 3rd Party Administrator's Requirements

My employer is self insured and uses Aetna as the third party administrator.  In my employer's summary plan description, it only says that you have to be 100 pounds over weight and nothing more and Aetna has their own list of additional requirements.  Which requirements would I have to go by?  The one from my employer or the one from Aetna? Thanks, Laura