a0d929ca_WSRP_v2_0_Specification__Statement_text
[#] CS113 [Section] 7.2 [Statement text] 
For security reasons related to exposing the existence of something the caller is not allowed to access, it is RECOMMENDED that a AccessDenied fault be generated both for the case of the supplied portletHandle not being a valid reference in the scope of the supplied registrationHandle and for the case of the user not having access to a valid reference (i.e. by definition access is denied when the Portlet reference is invalid).
WSRP v2.0 Specification
Statement text