As the registered owner of the UA, you are responsible for its activities. You must ensure that anyone operating your UA is competent and operates it safely and responsibly.

If you give your friend permission to use your registered UA, you will be held responsible if there are any contraventions to the rules.

However, if you want to transfer ownership to your friend, you need to de-register your UA, remove the registration label. Your friend will need to purchase a new registration label and complete the registration.