By default, only the owner of a virtual machine has full access to it. All other users are completely unaware of the machine (it will not even appear in the list of the available virtual machines for them). The owner of the virtual machine can change this by setting the virtual machine access rights for other users. The access rights include no-access, view, run, full access (see PRL_VM_ACCESS_FOR_OTHERS for the complete list). 

The PHT_ACCESS_RIGHTS handle is obtained by calling the PrlVmCfg_GetAccessRights or the PrlVmInfo_GetAccessRights function. An object returned by either function will contain access rights information for a specific virtual machine. You can use either function to obtain a handle depending on the application logic.