a0d929ca_WSRP_v2_0_Specification__Statement_text
[#] CS120 [Section] 7.4 [Statement text] 
The Consumer MUST inform the Producer that a Consumer Configured Portlet which does not use leasing will no longer be used by invoking either the destroyPortlets or the deregister operation and MUST NOT consider such a Portlet to have been destroyed until one of these operations has been successfully invoked for that Portlet.
WSRP v2.0 Specification
Statement text