Good Samaritan laws apply to anyone trying to assist in an emergency, including off duty doctors and nurses. The only way to be sued for trying to help is if you are the sole cause of the injury or if you cause further injury by taking unnecessary action.
First aid is a great thing to know. Even if you forget most of it there are still basic things that can save lives, basic scene survey and Airway Breathing Circulation Defibrilate (ABCD) for example.
Back to your hypothetical question.
I believe the correct course of action is to take your ski pole, put it in your freind's throat, and attempt to dislodge the gum from the airway.