Here is the flag to enable or to disable JSSE.

Oracle recommends that you keep this value set to true.  Starting WLS 12c, Even if the above option is set to false , it is ignored. The changes are neither persisted nor the Mbean value is also left unmodified....

Please also be aware of the below changes in SSL implementation in 12c version

1. Certicom has been removed from WebLogic Server 12.1.1 and is no longer supported.

2. JSSE is the only SSL implementation that is supported in WebLogic Server 12.1.1.

The following configuration changes have been made to be consistent with this support:

• The default for JSSEEnabled has been changed to true. Oracle recommends that you keep this value set to true.
• If JSSEEnabled is set to false, it will be ignored. That is, the MBean value will not be changed either in memory or the persisted config.xml file. WebLogic Server will continue to use JSSE, but will issue a warning.

Please refer to the below doc in OTN for more info...

Oracle Fusion Middleware What's New in Oracle WebLogic Server - 12c Release 1 (12.1.1)