The admin server and managed servers run on their own JVM processes.
Only managed servers started using a nodemanager can be stopped by the weblogic admin server.
Node Manager is a
Java utility that runs as separate process from WebLogic Server and allows you to perform common operations tasks for a Managed Server, regardless of its location with respect to its Administration Server.
http://e-docs.bea.com/wls/docs81/adminguide/nodemgr.html